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Cretoleptochromus archaicus gen. et sp. nov., a new genus of ant-like stone beetles in Upper Cretaceous Burmese amber (Coleoptera, Staphylinidae, Scydmaeninae)
Accepted Manuscript Cretoleptochromus archaicus gen. et sp. nov., a new genus of ant-like stone beetles in Upper Cretaceous Burmese amber (Coleoptera, Staphylinidae, Scydmaeninae) Chenyang Cai, Diying Huang PII:
S0195-6671(16)30027-1
DOI:
10.1016/j.cretres.2016.02.016
Reference:
YCRES 3357
To appear in:
Cretaceous Research
Received Date: 15 November 2015 Revised Date:
23 January 2016
Accepted Date: 27 February 2016
Please cite this article as: Cai, C., Huang, D., Cretoleptochromus archaicus gen. et sp. nov., a new genus of ant-like stone beetles in Upper Cretaceous Burmese amber (Coleoptera, Staphylinidae, Scydmaeninae), Cretaceous Research (2016), doi: 10.1016/j.cretres.2016.02.016. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Cretoleptochromus archaicus gen. et sp. nov., a new genus of ant-like stone beetles in Upper Cretaceous Burmese amber (Coleoptera, Staphylinidae, Scydmaeninae)
a
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Chenyang Cai a, Diying Huang b*
Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and
Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
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b
*
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Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
Corresponding author. Nanjing Institute of Geology and Palaeontology, Chinese Academy of
Sciences, 39 East Beijing Road, Nanjing 210008, China. E-mail address: [email protected] (D.
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Huang).
ACCEPTED MANUSCRIPT Abstract A new genus and species of the ant-like stone beetle supertribe Mastigitae, Cretoleptochromus archaicus gen. et sp. nov., is described and figured based on an exceptionally well-preserved individual in the Upper Cretaceous (lowermost Cenomanian, ca. 99 Ma) amber from Myanmar.
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Cretoleptochromus is undoubtedly placed in Mastigitae based on its distinctly geniculate antennae with strongly elongate antennal scape, and pointed labial palpomere III. Cretoleptochromus is most likely the sister taxon to the extinct Palaeoleptochromus O'Keefe from the Late Cretaceous Canadian
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amber. Cretoleptochromus shares with Clidicini the distinct posterior collar of pronotum; with Leptomastacini the presence of mesocoxal lateroventral bristles. The new discovery may help to
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elucidate the relationships among the Recent three tribes, particularly for Leptomastacini and Clidicini.
Mastigitae Clidicini
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Cenomanian
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Scydmaeninae
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Keywords:
taxonomy
ACCEPTED MANUSCRIPT 1. Introduction With nearly 4,900 species in over 100 (extant and extinct) genera, Scydmaeninae, or ant-like stone beetles, is a large and diverse group of Staphylinidae (Grebennikov and Newton, 2009). Scydmaenines have been regarded as an isolated family of Staphylinoidea for nearly two centuries,
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and only recently it was included in the hyper-diverse family Staphylinidae based on a
comprehensive phylogenetic analysis (Grebennikov and Newton, 2009). Scydmaeninae comprises one extinct (Hapsomelitae) and three extant supertribes (Mastigitae, Cephenniitae and Scydmaenitae).
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The poorly-defined Hapsomelitae is known only from several species in Cretaceous Burmese amber (Poinar and Brown, 2004; Chatzimanolis et al., 2010), but their relationships and systematic position
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within Scydmaeninae remain elusive. Mastigitae is a small group of less than a hundred species grouped in nine genera and two extinct genera, and phylogenetic relationships of this supertribe have been recently studied (Jałoszyński, 2012). Cephenniitae, with 26 genera and less than 500 species placed in three tribes, is a well-supported monophyletic lineage (Jałoszyński, 2014). With
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approximately 4400 species and 65 genera, Scydmaenitae is the largest supertribe, and it is most problematic group in terms of relationships between genera. Mastigitae are divided into three poorly-defined tribes: Clidicini, Leptomastacini and Mastigini.
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Clidicini, with body length ranging from less than 2 mm to 10 mm, shows disjunctive distributions:
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Clidicus Laporte occurs in southeastern Asia and northern Australia, Leptochromus Motschulsky is distributed from Mexico to Brazil, and Papusus Casey in southwestern United States and Mexico (Jałoszyński, 2012). In addition, two fossil genera of Clidicini are known from the Late Cretaceous Canadian amber (Palaeoleptochromus O'Keefe) and the Eocene Baltic amber (Euroleptochromus Jałoszyński). It is noteworthy that the placement of Papusus in Clidicini is suggested to be problematic (Jałoszyński, 2012). Leptomastacini consists of small, flattened and often lightly pigmented beetles occurring in Western Palaearctic region. Mastigini, comprising wingless and usually conspicuous beetles with elongate legs and antennae, is the largest group of Mastigitae.
ACCEPTED MANUSCRIPT Genera of Mastigitae are characterized by the following combination of characters: antennomere I strongly elongate, distinctly longer than antennomere II; antennae geniculate between antennomeres I and II; labial palpomere III pointed; maxillary palps longer than head; and eyes located in the anterior part of the head (O'Keefe et al, 1997; O'Keefe, 2005; Jałoszyński, 2012).
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Fossil scydmaenines are not uncommon, especially preserved in amber as small-bodied beetles. Scydmaenine fossils are known from Baltic, Burmese, Canadian, Dominican, Lebanese, Mexican, Sicilian and Spanish ambers (O'Keefe et al., 1997; Newton and Franz, 1998; Chatzimanolis et al.,
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2010; Jałoszyński, 2012; Jałoszyński and Peris, 2016; Kirejtshuk et al., 2013; Peris et al., 2014). The Mesozoic scydmaenines are only known from ambers, including those formally described based on
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well-preserved individuals in Burmese, Canadian, French, and Spanish ambers. The oldest known scydmaenine fossil, Kachinus magnificus Peris, Chatzimanolis and Delclòs, was described from the Early Cretaceous (early Albian) Spanish amber (Peris et al., 2014). Relatively numerous scydmaenines are from the Late Cretaceous (earliest Cenomanian, ca. 99 Ma) Burmese amber. The
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first genus described from the Burmese amber, Hapsomela Poinar and Brown, was attributed to a new supertribe Hapsomelitae (Poinar and Brown, 2004), and later two more genera from the same deposits, Ektatotrichia Chatzimanolis, Engel and Newton and Electroatopos Chatzimanolis, Engel
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and Newton, were placed in this group (Chatzimanolis et al., 2010). However, key features such as
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the head capsule and maxillary palps of Hapsomela are distinctly different from those of Ektatotrichia and Electroatopos, suggesting that Hapsomelitae is a heterogeneous group (Jałoszyński, 2012). The fourth genus from Burmese amber, Kachinus Chatzimanolis, Engel and Newton, was regarded as incertae sedis within Scydmaenitae, showing possible affinities with the extant tribes Eutheiini or Cephenniini (Chatzimanolis et al., 2010). O’Keefe et al. (1997) described a new genus and species belonging to Mastigitae, Palaeoleptochromus schaufussi O’Keefe, from the Late Cretaceous (Campanian, ca. 79 Ma) Canadian amber. Recently, Kirejtshuk et al. (2015) described a new species (Clidicus cretaceus Kirejtshuk, Kurbatov and Nel) belonging to the extant genus
ACCEPTED MANUSCRIPT Clidicus from the Lower Cretaceous (latest Albian to earliest Cenomanian) French amber of Archingeay. In addition, several undescribed specimens of Scydmaeninae are known from the Early Cretaceous Lebanese amber (Kirejtshuk et al., 2013). Like fossil scydmaenines, fossils belonging to Mastigitae are not rare, with three species known
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from both Mesozoic and Cenozoic ambers (O'Keefe et al., 1997; O'Keefe, 2002; Jałoszyński, 2012). The oldest is Palaeoleptochromus schaufussi from the Campanian Canadian amber (O’Keefe et al., 1997). The other two Cenozoic species are the Miocene Mexican amber (Leptochromus
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palaeomexicanus O'Keefe, 2002) and the late Eocene Baltic amber (Euroleptochromus sabathi Jałoszyński, 2012). All species mentioned above were placed in Clidicini, which is strongly
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supported by phylogenetic analyses combining morphological characters of both extant and extinct taxa (O'Keefe, 2002; Jałoszyński, 2012). Jałoszyński (2012) reviewed the fossil record of Mastigitae. Scydmaenines in Burmese amber are remarkably abundant and diverse. In the present paper, we describe a new genus and species of Scydmaeninae based on an individual preserved in Burmese
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amber. The new genus has characters belonging to the extant tribes Clidicini and Leptomastacini, but cannot be placed in either of them.
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2. Material and methods
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The sole specimen is from amber deposits in the Hukawng Valley of northern Myanmar. An overview of the amber deposit and its geological settings was made by Grimaldi et al. (2002) and Ross et al. (2010). Recent U-Pb zircon dating constrained the Burmese amber to a maximum age of 98.79 ± 0.62 Ma, which is equivalent to the Late Cretaceous (Cenomanian, Shi et al., 2012). The fossil-containing amber was prepared using a mini table-saw, polished with emery papers with different grain sizes, and finally lustrated with polishing powder. Photographs were taken using a Zeiss Discovery V20 stereo microscope and a Zeiss Axio Imager 2 compound microscope with a digital camera attached respectively. Photographs with green background are taken using
ACCEPTED MANUSCRIPT fluorescence as light source attached to a Zeiss Axio Imager 2 compound microscope.
3. Systematic paleontology Order: Coleoptera Linnaeus, 1758
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Family: Staphylinidae Latreille, 1802 Subfamily: Scydmaeninae Leach, 1815 Supertribe: Mastigitae Fleming, 1821
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Genus: Cretoleptochromus gen. nov.
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Tribe: Unknown
Type species. Cretoleptochromus archaicus gen. et sp. nov., here designated.
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Etymology. The genus name is composed of the prefix Creto- derived from the Cretaceous and the extant genus Leptochromus. The gender of the name is masculine.
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Diagnosis. Body relatively large for scydmaenines (ca. 3.55 mm long), elongate, with well-marked
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constrictions between head and pronotum and between pronotum and elytra. Head (including mandibles) slightly longer than wide, with relatively small, anteriorly located compound eyes. Anterior margin of labrum V-shaped. Frontoclypeal suture developed. Maxillary palpus very long, with palpomere I minute and elongate; palpomere II strongly elongate, nearly parallel-sided in distal half, slightly bent near middle, without mesal protuberance; palpomere III very long and gradually broadening towards apex; palpomere IV sub-conical, nearly parallel-sided in basal half, distinctly tapered toward apex, with pointed apex. Labial palpus much shorter than maxillary palpus, labial palpomere I elongate, slightly curved; labial palpomere II gradually widened toward apex, with long
ACCEPTED MANUSCRIPT apical setae; labial palpomere III long, acuminate. Lacinia and galea densely setose. Antenna shorter than body length, geniculate between scapus and pedicellus, with long bristles; scape slightly shorter than head; pedicellus much shorter than scapus; flagellomeres elongate, each distinctly broadening distally. Antennal insertion exposed in dorsal view, just at a line draw between anterior margins of
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eyes. Pronotum longer than wide, without defined anterior angles, posterior margin arcuate; posterior collar well-defined, separated from disc by a basal transverse groove; prosternum long.
Mesoscutellum small; elytra elongate, with well-marked humeri, with moderately deep punctate
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striae; mesoventrite with a narrow longitudinal mesoventral intercoxal carina. Metaventrite long, with a relatively wide longitudinal median carina, its posterior margin slightly concave. Abdomen
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with five ventrites, ventrite V longest, subtriangular, with unmodified apical margin between metacoxae. Legs very long and robust; procoxae contiguous, mesocoxae narrowly separated, metacoxae widely separated; mesocoxae bearing dense bristles along lateral margin; metacoxal plates developed; all femora strongly clavate, pro- and mesofemora each with one bristle on ventral
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margin; all tibiae slender, nearly straight; all tarsi 5-segmented, tarsomeres nearly cylindrical.
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(Figs. 1–3)
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Cretoleptochromus archaicus sp. nov.
Etymology. The Latin word (adapted from Greek) ‘‘archaicus’’ means ancient.
Holotype. NIGP163304, earliest Cenomanian, Hukawng Valley, northern Myanmar; deposited in the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China.
Diagnosis. As for the genus (vide supra).
ACCEPTED MANUSCRIPT Description. Female. Body elongate (Fig. 1), 3.55 mm long, slender and brown, including vestiture. Head broadest slightly behind eyes (Figs. 2A and 3A); head length 0.67 mm, head width 0.62 mm; vertex short and densely setose, convex on sides and flattened in middle; one long seta located at posterior margin of eye, four long setae behind each antennal insertion, two long setae on
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posterolateral margin of head, and a pair of long setae on neck (Fig. 3A); tempora much longer than length of eye in dorsal view, strongly rounded; frons slightly lowering towards clypeus, frons broad and flattened; anterior margin of clypeus convex; labrum (Fig. 2A) with anterior margin bearing
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about eight long setae; eyes small and strongly convex, coarsely faceted (Fig. 2A); mandible prominent, with sharp apex and two preapical teeth (Fig. 2A, 2B); maxillary palpus long (Fig. 3D,
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3E), palpomere II 0.31 mm, palpomere III 0.26 mm, palpomere IV 0.18 mm; labial palpus much shorter than maxillary palpus (Figs. 2B, 3C), labial palpomere II about 1.6 times as long as palpomere I, palpomere III much narrower than palpomere II, about 0.7 times as long as palpomere II. Antenna (Fig. 3F) 2.36 mm long, lengths of antennomeres: I, 0.53 mm; II, 0.14 mm; III, 0.16 mm;
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IV, 0.21 mm; V, 0.18 mm; VI, 0.19 mm; VII, 0.19 mm; VIII, 0.19 mm; IX, 0.18 mm; X, 0.18 mm; XI, 0.21 mm; scape strongly elongate and slightly broadening toward apex, slightly shorter than head length (including mandibles); pedicel 0.26 times as long as scape; all flagellomeres more or less
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elongate; each antennomere with several long and dense short setae.
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Pronotum (Fig. 3A) 0.74 mm long and 0.66 mm wide, broadest across anterolateral margins, narrowing posteriorly, anterior and lateral margins rounded, posterior margin slightly arcuate, sides in posterior 1/5 indistinctly constricted; base with distinct transverse groove separating very short posterior collar. Vestiture dense, short and erect. Prothoracic hypomeron not delimited; prosternum elongate, prosternal process sharp, not separating procoxae; prosternum covered with dense short and several long setae. Elytra (Fig. 2C) 2.10 mm long, each 0.51 mm wide; broadest at anterior one sixth; each elytron with well-developed humerus, five longitudinal, deeply punctate striae and sharp elytral apex;
ACCEPTED MANUSCRIPT vestiture similar to that on pronotum, setae slightly longer. Mesoscutellum small, subtriangular. Mesoventrite short, with narrow mesoventral carina separating mesocoxae. Metaventrite very large, broader than long, with a complete indistinctive metaventral carina; sides of ventrite convex. Surface of ventrite covered with dense suberect setae.
ventrite II. Abdomen covered with similar vestiture as metaventrite.
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Abdomen longer than mesoventrite and metaventrite together; ventrite I distinctly longer than
Legs slender. All coxae subconical in shape (Fig. 3B), pro- and mesocoxae elongate, each
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procoxa with three long setae along posterolateral margin; each mesocoxa with a rows of (more than 15) laterally-directed long setae, metacoxae short. Pro- and mesotrochanters rounded,
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metatrochanters long, trochanterofemoral connection strongly oblique; each pro- and mesotrochanter with a long posteriorly-directed bristle. All femora strongly clavate. Pro- and mesofemur each with a long ventrally-directed bristle. Tibiae about as long as femora, slender; protibiae slightly curved, distal half with dense ventrally-directed setae; mesotibiae very slightly curved, distal third with dense
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ventrally-directed setae; metatibiae straight; all tibiae covered with vestiture similar to that on femora. Tarsi slender (e.g., Fig. 3G), all slightly longer than half length of tibiae; all tarsomeres I–IV
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4. Discussion
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successively shorter posteriorly, and tarsomere V longest. Pretarsal claws simple.
The new genus Cretoleptochromus is placed in the extant Mastigitae on the basis of the geniculate antennae with remarkably long antennomere I, elongate maxillary palps, pointed labial palpomere III, and anteriorly-located eyes (O'Keefe, 2005; Jałoszyński, 2012). Among Mastigitae, Cretoleptochromus can be easily ruled out from Mastigini by lacking spins on scape and pedicel and more or less dilated apical maxillary palpomere. Cretoleptochromus appears to intermingle features belonging to two extant tribes: Clidicini and Leptomastacini. In particular, it shares with Clidicini the following characters: the posterior collar of pronotum distinct, the compound eyes well-developed
ACCEPTED MANUSCRIPT (composed of several dozens of ommatidia), and the antennal flagellomeres (except XI) all elongate. It shares with Leptomastacini the presence of mesocoxal lateroventral bristles. Recent phylogenetic analyses based on adult morphological characters questioned the monophyly of Clidicini because of an alternative placement of Nearctic Papusus as a sister taxon to Leptomastacini + [Clidicus +
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(Palaeoleptochromus + (Euroleptochromus + Leptochromus))] (Jałoszyński, 2012). The unique apomorphy of Papusus and Leptomastacini is the presence of mesocoxal lateroventral bristles (Jałoszyński, 2012), a character also well shown in Cretoleptochromus. Therefore, it is not easy to
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place the new genus in Clidicini or Leptomastacini; we here leave the new genus as incertae sedis within the supertribe Mastigitae. In particular, Cretoleptochromus is separated from Papusus by
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having elongate apical maxillary palpomere, rows of punctures on elytron, and slender tarsi; from Clidicus by elongate maxillary palpomeres III and IV (not enlarged), elongate pronotum, and slender legs; from Leptochromus by its unmodified maxillary palpi with pointed maxillary palpomere IV; from Leptomastax by elongate maxillary palpi with pointed maxillary palpomere IV, short labial
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palpomere III, and slender antennae and legs; and from Ablepton Frivaldszky (Leptomastacini) by well-developed eyes (eyes rudimentary in Ablepton). Among all genera of Mastigitae, the Cretoleptochromus closely resembles the extinct genus
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Palaeoleptochromus from the Late Cretaceous Canadian amber (O’Keefe et al., 1997). They share
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similar body shape with long antennae and legs, unmodified maxillary palpi with pointed maxillary palpomere IV, widely separated antennal insertions, anteriorly-widest pronotum, contiguous procoxae, and widely separated metacoxae. However, Cretoleptochromus differs from Palaeoleptochromus in having a posteriorly-broadened head (narrowing posteriorly in Palaeoleptochromus), more elongate, bullet-shaped maxillary palpomere 4 (shorter and conical in Palaeoleptochromus), and elongate antennal segments (antennomeres VII–X subtriangular in Palaeoleptochromus). Jałoszyński (2012) suggested that the clade [Palaeoleptochromus + (Euroleptochromus + Leptochromus)] is well-supported by four distinguishing characters: 1) the
ACCEPTED MANUSCRIPT presence of postgenal setae; 2) the maxillary palpomere II nearly parallel-sided in distal half; 3) the presence of protrochanteral, and 4) the presence of profemoral bristles. However, only the second character (the maxillary palpomere II nearly parallel-sided in distal half) can be confirmed for Palaeoleptochromus as shown in O’Keefe et al. (1997). More detailed observations of the holotype
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of Palaeoleptochromus schaufussi are needed to confirm the characters mentioned above. In Cretoleptochromus, the postgenal setae appear to be present, although there is no sign of postgenal process (an interesting character found in Palaeoleptochromus and Leptochromus); the maxillary
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palpomere II is nearly parallel-sided in its distal half. It is noteworthy that the protrochanteral and profemoral bristles of Cretoleptochromus are indeed present, but the number of bristles is greatly
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reduced compared to those of the extinct Palaeoleptochromus or the extant Leptochromus. In Cretoleptochromus, there is only one protrochanteral bristle and one profemoral bristle located near the base of profemur. By contrast, there are seven protrochanteral bristles and eight profemoral bristles along the basal half of profemur in Euroleptochromus (Jałoszyński, 2012), and there are one
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protrochanteral bristle and three profemoral bristles in a Palaeoleptochromus species (Leptochromus laselva Lord, Carlton and Leschen; Lord et al., 2014). Jałoszyński (2012) also suggested that Euroleptochromus, Palaeoleptochromus and Leptochromus share highly derived structures on
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postgenae and maxillary palps, probably as part of a specialized feeding or prey capture mechanism.
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The statement is true for Euroleptochromus and Leptochromus as they both possess postgenal process and setal process on maxillary palpomere II, but not for the Cretaceous Palaeoleptochromus. The maxillary palpus of the new genus Cretoleptochromus has no modifications on maxillary palpomere II, which is similar to that of Palaeoleptochromus. The biogeography and mouthpart evolution within Clidicini is tentatively discussed by Jałoszyński (2012), but several specific aspects are still open to question. The new fossil of a slightly older age than that of Palaeoleptochromus may help to clarify this problem. Recently, a new species belonging to the extant genus Clidicus, Clidicus cretaceus, is described
ACCEPTED MANUSCRIPT from the Lower Cretaceous French amber (Kirejtshuk et al., 2015). Kirejtshuk et al. (2015) placed the fossil in Clidicus as supported by distinct longitudinal rows of punctures (on elytron) which are slightly depressed and weakly clavate femora as defined by O’Keefe (2002). However, compared to members of Clidicus, the fossil has much larger eyes that located medially on sides of the head,
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elongate maxillary palpomere III that gradually widened toward apex, and much longer antennae with elongate antennomeres. In Clidicus, the eyes are small, located at anterior part of the head; the apical two maxillary palpomeres are strongly enlarged, and maxillary palpomere III is distinctly
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broader than maxillary palpomere IV. The fossil is definitely not a member of Clidicus; it probably represents a new genus close to Clidicus or the new genus Cretoleptochromus, but more characters
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should be checked to make a more comprehensive comparison, such as postgenal setae, labial palpi, protrochanteral and profemoral bristles, mesocoxal lateroventral bristles, and many other features.
5. Concluding remarks
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The new discovery of a new genus and species of the supertribe Mastigitae from the Upper Cretaceous Burmese amber highlights the palaeodiversity of Mastigitae and even for Scydmaeninae in the Mesozoic. It also represents the oldest fossil record for the supertribe Mastigitae. More
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importantly, the new genus is closely related to the extinct Palaeoleptochromus O'Keefe from the
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Late Cretaceous Canadian amber, bearing significant biogeographic implications for the tribe Clidicini and the supertribe Mastigitae. A comprehensive phylogenetic analysis integrating all extinct (especially Mesozoic fossils) and extant genera of Mastigitae is necessary for understanding the relationships among the Recent three tribes, particularly for Leptomastacini and Clidicini.
Acknowledgements We are grateful to two anonymous reviewers for their helpful comments on the manuscript. The work has been supported by the National Basic Research Program of China (2012CB821903), the
ACCEPTED MANUSCRIPT National Natural Science Foundation of China (J1210006), and the open grant of the Key Laboratory of Economic Stratigraphy and Palaeogeography (2016KF07).
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in Early Cretaceous Spanish amber. Cretaceous Research 48, 85–95. Poinar Jr., G., Brown, A.E., 2004. A new subfamily of Cretaceous antlike stone beetles (Coleoptera: Scydmaenidae: Hapsomelinae) with an extra leg segment. Proceedings of the Entomological Society of Washington 106, 789–796. Ross, A.J., Mellish, C., York, P., Crighton, B., 2010. Burmese amber. In: Penney, D. (Ed.), Biodiversity of Fossils in Amber from the Major World Deposits. Siri Scientific Press, Manchester, pp. 208–235. Shi, G., Grimaldi, D.A., Harlow, G.E., Wang, J., Wang, J., Yang, M., Lei, W., Li, Q., Li, X., 2012.
ACCEPTED MANUSCRIPT Age constraint on Burmese amber based on U-Pb dating of zircons. Cretaceous Research 37, 155–163.
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[FIGURE CAPTIONS]
Fig. 1. Photograph of holotype (NIGP163304) of Cretoleptochromus archaicus gen. et sp. nov., in
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Upper Cretaceous amber from northern Myanmar. A. dorsal view; B. ventral view. Scale bars: 1 mm.
Fig. 2. Close-ups of holotype (NIGP163304) of Cretoleptochromus archaicus gen. et sp. nov., under
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normal light. A. head, showing eyes, antennal insertions and labrum; B. ventral view of anterior part of head, showing the left labial palpus and mandibles; C. elytra, showing punctate striae. Scale bars: 200 µm in A and B, 500 µm in C.
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Fig. 3. Close-ups of holotype (NIGP163304) of Cretoleptochromus archaicus gen. et sp. nov., under Zeiss Axio Imager 2 compound microscope using fluorescence as light source. A. dorsal view of head and pronotum; B. ventral view of thorax, showing contiguous procoxae and distinctly separated
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meso- and metacoxae; C. ventral view of anterior part of head, showing setose lacinia and galea; D.
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ventral view of the left maxillary palpus; E. dorsal view of the right maxillary palpus; F. right antenna and part of right maxillary palpus; G. left metatarsus. a, antennomere; e, eye; fcs, fontoclypeal suture; lp, labial palpomere; ma, mandible; mcp, metacoxal plate; mp, maxillary palpomere; Scale bars: 500 µm in A, B and F, 200 µm in others.
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S0195-6671(16)30027-1
DOI:
10.1016/j.cretres.2016.02.016
Reference:
YCRES 3357
To appear in:
Cretaceous Research
Received Date: 15 November 2015 Revised Date:
23 January 2016
Accepted Date: 27 February 2016
Please cite this article as: Cai, C., Huang, D., Cretoleptochromus archaicus gen. et sp. nov., a new genus of ant-like stone beetles in Upper Cretaceous Burmese amber (Coleoptera, Staphylinidae, Scydmaeninae), Cretaceous Research (2016), doi: 10.1016/j.cretres.2016.02.016. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Cretoleptochromus archaicus gen. et sp. nov., a new genus of ant-like stone beetles in Upper Cretaceous Burmese amber (Coleoptera, Staphylinidae, Scydmaeninae)
a
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Chenyang Cai a, Diying Huang b*
Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and
Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and
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b
*
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Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
Corresponding author. Nanjing Institute of Geology and Palaeontology, Chinese Academy of
Sciences, 39 East Beijing Road, Nanjing 210008, China. E-mail address: [email protected] (D.
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Huang).
ACCEPTED MANUSCRIPT Abstract A new genus and species of the ant-like stone beetle supertribe Mastigitae, Cretoleptochromus archaicus gen. et sp. nov., is described and figured based on an exceptionally well-preserved individual in the Upper Cretaceous (lowermost Cenomanian, ca. 99 Ma) amber from Myanmar.
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Cretoleptochromus is undoubtedly placed in Mastigitae based on its distinctly geniculate antennae with strongly elongate antennal scape, and pointed labial palpomere III. Cretoleptochromus is most likely the sister taxon to the extinct Palaeoleptochromus O'Keefe from the Late Cretaceous Canadian
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amber. Cretoleptochromus shares with Clidicini the distinct posterior collar of pronotum; with Leptomastacini the presence of mesocoxal lateroventral bristles. The new discovery may help to
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elucidate the relationships among the Recent three tribes, particularly for Leptomastacini and Clidicini.
Mastigitae Clidicini
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Cenomanian
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Scydmaeninae
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Keywords:
taxonomy
ACCEPTED MANUSCRIPT 1. Introduction With nearly 4,900 species in over 100 (extant and extinct) genera, Scydmaeninae, or ant-like stone beetles, is a large and diverse group of Staphylinidae (Grebennikov and Newton, 2009). Scydmaenines have been regarded as an isolated family of Staphylinoidea for nearly two centuries,
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and only recently it was included in the hyper-diverse family Staphylinidae based on a
comprehensive phylogenetic analysis (Grebennikov and Newton, 2009). Scydmaeninae comprises one extinct (Hapsomelitae) and three extant supertribes (Mastigitae, Cephenniitae and Scydmaenitae).
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The poorly-defined Hapsomelitae is known only from several species in Cretaceous Burmese amber (Poinar and Brown, 2004; Chatzimanolis et al., 2010), but their relationships and systematic position
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within Scydmaeninae remain elusive. Mastigitae is a small group of less than a hundred species grouped in nine genera and two extinct genera, and phylogenetic relationships of this supertribe have been recently studied (Jałoszyński, 2012). Cephenniitae, with 26 genera and less than 500 species placed in three tribes, is a well-supported monophyletic lineage (Jałoszyński, 2014). With
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approximately 4400 species and 65 genera, Scydmaenitae is the largest supertribe, and it is most problematic group in terms of relationships between genera. Mastigitae are divided into three poorly-defined tribes: Clidicini, Leptomastacini and Mastigini.
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Clidicini, with body length ranging from less than 2 mm to 10 mm, shows disjunctive distributions:
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Clidicus Laporte occurs in southeastern Asia and northern Australia, Leptochromus Motschulsky is distributed from Mexico to Brazil, and Papusus Casey in southwestern United States and Mexico (Jałoszyński, 2012). In addition, two fossil genera of Clidicini are known from the Late Cretaceous Canadian amber (Palaeoleptochromus O'Keefe) and the Eocene Baltic amber (Euroleptochromus Jałoszyński). It is noteworthy that the placement of Papusus in Clidicini is suggested to be problematic (Jałoszyński, 2012). Leptomastacini consists of small, flattened and often lightly pigmented beetles occurring in Western Palaearctic region. Mastigini, comprising wingless and usually conspicuous beetles with elongate legs and antennae, is the largest group of Mastigitae.
ACCEPTED MANUSCRIPT Genera of Mastigitae are characterized by the following combination of characters: antennomere I strongly elongate, distinctly longer than antennomere II; antennae geniculate between antennomeres I and II; labial palpomere III pointed; maxillary palps longer than head; and eyes located in the anterior part of the head (O'Keefe et al, 1997; O'Keefe, 2005; Jałoszyński, 2012).
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Fossil scydmaenines are not uncommon, especially preserved in amber as small-bodied beetles. Scydmaenine fossils are known from Baltic, Burmese, Canadian, Dominican, Lebanese, Mexican, Sicilian and Spanish ambers (O'Keefe et al., 1997; Newton and Franz, 1998; Chatzimanolis et al.,
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2010; Jałoszyński, 2012; Jałoszyński and Peris, 2016; Kirejtshuk et al., 2013; Peris et al., 2014). The Mesozoic scydmaenines are only known from ambers, including those formally described based on
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well-preserved individuals in Burmese, Canadian, French, and Spanish ambers. The oldest known scydmaenine fossil, Kachinus magnificus Peris, Chatzimanolis and Delclòs, was described from the Early Cretaceous (early Albian) Spanish amber (Peris et al., 2014). Relatively numerous scydmaenines are from the Late Cretaceous (earliest Cenomanian, ca. 99 Ma) Burmese amber. The
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first genus described from the Burmese amber, Hapsomela Poinar and Brown, was attributed to a new supertribe Hapsomelitae (Poinar and Brown, 2004), and later two more genera from the same deposits, Ektatotrichia Chatzimanolis, Engel and Newton and Electroatopos Chatzimanolis, Engel
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and Newton, were placed in this group (Chatzimanolis et al., 2010). However, key features such as
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the head capsule and maxillary palps of Hapsomela are distinctly different from those of Ektatotrichia and Electroatopos, suggesting that Hapsomelitae is a heterogeneous group (Jałoszyński, 2012). The fourth genus from Burmese amber, Kachinus Chatzimanolis, Engel and Newton, was regarded as incertae sedis within Scydmaenitae, showing possible affinities with the extant tribes Eutheiini or Cephenniini (Chatzimanolis et al., 2010). O’Keefe et al. (1997) described a new genus and species belonging to Mastigitae, Palaeoleptochromus schaufussi O’Keefe, from the Late Cretaceous (Campanian, ca. 79 Ma) Canadian amber. Recently, Kirejtshuk et al. (2015) described a new species (Clidicus cretaceus Kirejtshuk, Kurbatov and Nel) belonging to the extant genus
ACCEPTED MANUSCRIPT Clidicus from the Lower Cretaceous (latest Albian to earliest Cenomanian) French amber of Archingeay. In addition, several undescribed specimens of Scydmaeninae are known from the Early Cretaceous Lebanese amber (Kirejtshuk et al., 2013). Like fossil scydmaenines, fossils belonging to Mastigitae are not rare, with three species known
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from both Mesozoic and Cenozoic ambers (O'Keefe et al., 1997; O'Keefe, 2002; Jałoszyński, 2012). The oldest is Palaeoleptochromus schaufussi from the Campanian Canadian amber (O’Keefe et al., 1997). The other two Cenozoic species are the Miocene Mexican amber (Leptochromus
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palaeomexicanus O'Keefe, 2002) and the late Eocene Baltic amber (Euroleptochromus sabathi Jałoszyński, 2012). All species mentioned above were placed in Clidicini, which is strongly
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supported by phylogenetic analyses combining morphological characters of both extant and extinct taxa (O'Keefe, 2002; Jałoszyński, 2012). Jałoszyński (2012) reviewed the fossil record of Mastigitae. Scydmaenines in Burmese amber are remarkably abundant and diverse. In the present paper, we describe a new genus and species of Scydmaeninae based on an individual preserved in Burmese
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amber. The new genus has characters belonging to the extant tribes Clidicini and Leptomastacini, but cannot be placed in either of them.
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2. Material and methods
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The sole specimen is from amber deposits in the Hukawng Valley of northern Myanmar. An overview of the amber deposit and its geological settings was made by Grimaldi et al. (2002) and Ross et al. (2010). Recent U-Pb zircon dating constrained the Burmese amber to a maximum age of 98.79 ± 0.62 Ma, which is equivalent to the Late Cretaceous (Cenomanian, Shi et al., 2012). The fossil-containing amber was prepared using a mini table-saw, polished with emery papers with different grain sizes, and finally lustrated with polishing powder. Photographs were taken using a Zeiss Discovery V20 stereo microscope and a Zeiss Axio Imager 2 compound microscope with a digital camera attached respectively. Photographs with green background are taken using
ACCEPTED MANUSCRIPT fluorescence as light source attached to a Zeiss Axio Imager 2 compound microscope.
3. Systematic paleontology Order: Coleoptera Linnaeus, 1758
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Family: Staphylinidae Latreille, 1802 Subfamily: Scydmaeninae Leach, 1815 Supertribe: Mastigitae Fleming, 1821
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Genus: Cretoleptochromus gen. nov.
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Tribe: Unknown
Type species. Cretoleptochromus archaicus gen. et sp. nov., here designated.
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Etymology. The genus name is composed of the prefix Creto- derived from the Cretaceous and the extant genus Leptochromus. The gender of the name is masculine.
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Diagnosis. Body relatively large for scydmaenines (ca. 3.55 mm long), elongate, with well-marked
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constrictions between head and pronotum and between pronotum and elytra. Head (including mandibles) slightly longer than wide, with relatively small, anteriorly located compound eyes. Anterior margin of labrum V-shaped. Frontoclypeal suture developed. Maxillary palpus very long, with palpomere I minute and elongate; palpomere II strongly elongate, nearly parallel-sided in distal half, slightly bent near middle, without mesal protuberance; palpomere III very long and gradually broadening towards apex; palpomere IV sub-conical, nearly parallel-sided in basal half, distinctly tapered toward apex, with pointed apex. Labial palpus much shorter than maxillary palpus, labial palpomere I elongate, slightly curved; labial palpomere II gradually widened toward apex, with long
ACCEPTED MANUSCRIPT apical setae; labial palpomere III long, acuminate. Lacinia and galea densely setose. Antenna shorter than body length, geniculate between scapus and pedicellus, with long bristles; scape slightly shorter than head; pedicellus much shorter than scapus; flagellomeres elongate, each distinctly broadening distally. Antennal insertion exposed in dorsal view, just at a line draw between anterior margins of
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eyes. Pronotum longer than wide, without defined anterior angles, posterior margin arcuate; posterior collar well-defined, separated from disc by a basal transverse groove; prosternum long.
Mesoscutellum small; elytra elongate, with well-marked humeri, with moderately deep punctate
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striae; mesoventrite with a narrow longitudinal mesoventral intercoxal carina. Metaventrite long, with a relatively wide longitudinal median carina, its posterior margin slightly concave. Abdomen
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with five ventrites, ventrite V longest, subtriangular, with unmodified apical margin between metacoxae. Legs very long and robust; procoxae contiguous, mesocoxae narrowly separated, metacoxae widely separated; mesocoxae bearing dense bristles along lateral margin; metacoxal plates developed; all femora strongly clavate, pro- and mesofemora each with one bristle on ventral
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margin; all tibiae slender, nearly straight; all tarsi 5-segmented, tarsomeres nearly cylindrical.
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(Figs. 1–3)
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Cretoleptochromus archaicus sp. nov.
Etymology. The Latin word (adapted from Greek) ‘‘archaicus’’ means ancient.
Holotype. NIGP163304, earliest Cenomanian, Hukawng Valley, northern Myanmar; deposited in the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China.
Diagnosis. As for the genus (vide supra).
ACCEPTED MANUSCRIPT Description. Female. Body elongate (Fig. 1), 3.55 mm long, slender and brown, including vestiture. Head broadest slightly behind eyes (Figs. 2A and 3A); head length 0.67 mm, head width 0.62 mm; vertex short and densely setose, convex on sides and flattened in middle; one long seta located at posterior margin of eye, four long setae behind each antennal insertion, two long setae on
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posterolateral margin of head, and a pair of long setae on neck (Fig. 3A); tempora much longer than length of eye in dorsal view, strongly rounded; frons slightly lowering towards clypeus, frons broad and flattened; anterior margin of clypeus convex; labrum (Fig. 2A) with anterior margin bearing
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about eight long setae; eyes small and strongly convex, coarsely faceted (Fig. 2A); mandible prominent, with sharp apex and two preapical teeth (Fig. 2A, 2B); maxillary palpus long (Fig. 3D,
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3E), palpomere II 0.31 mm, palpomere III 0.26 mm, palpomere IV 0.18 mm; labial palpus much shorter than maxillary palpus (Figs. 2B, 3C), labial palpomere II about 1.6 times as long as palpomere I, palpomere III much narrower than palpomere II, about 0.7 times as long as palpomere II. Antenna (Fig. 3F) 2.36 mm long, lengths of antennomeres: I, 0.53 mm; II, 0.14 mm; III, 0.16 mm;
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IV, 0.21 mm; V, 0.18 mm; VI, 0.19 mm; VII, 0.19 mm; VIII, 0.19 mm; IX, 0.18 mm; X, 0.18 mm; XI, 0.21 mm; scape strongly elongate and slightly broadening toward apex, slightly shorter than head length (including mandibles); pedicel 0.26 times as long as scape; all flagellomeres more or less
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elongate; each antennomere with several long and dense short setae.
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Pronotum (Fig. 3A) 0.74 mm long and 0.66 mm wide, broadest across anterolateral margins, narrowing posteriorly, anterior and lateral margins rounded, posterior margin slightly arcuate, sides in posterior 1/5 indistinctly constricted; base with distinct transverse groove separating very short posterior collar. Vestiture dense, short and erect. Prothoracic hypomeron not delimited; prosternum elongate, prosternal process sharp, not separating procoxae; prosternum covered with dense short and several long setae. Elytra (Fig. 2C) 2.10 mm long, each 0.51 mm wide; broadest at anterior one sixth; each elytron with well-developed humerus, five longitudinal, deeply punctate striae and sharp elytral apex;
ACCEPTED MANUSCRIPT vestiture similar to that on pronotum, setae slightly longer. Mesoscutellum small, subtriangular. Mesoventrite short, with narrow mesoventral carina separating mesocoxae. Metaventrite very large, broader than long, with a complete indistinctive metaventral carina; sides of ventrite convex. Surface of ventrite covered with dense suberect setae.
ventrite II. Abdomen covered with similar vestiture as metaventrite.
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Abdomen longer than mesoventrite and metaventrite together; ventrite I distinctly longer than
Legs slender. All coxae subconical in shape (Fig. 3B), pro- and mesocoxae elongate, each
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procoxa with three long setae along posterolateral margin; each mesocoxa with a rows of (more than 15) laterally-directed long setae, metacoxae short. Pro- and mesotrochanters rounded,
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metatrochanters long, trochanterofemoral connection strongly oblique; each pro- and mesotrochanter with a long posteriorly-directed bristle. All femora strongly clavate. Pro- and mesofemur each with a long ventrally-directed bristle. Tibiae about as long as femora, slender; protibiae slightly curved, distal half with dense ventrally-directed setae; mesotibiae very slightly curved, distal third with dense
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ventrally-directed setae; metatibiae straight; all tibiae covered with vestiture similar to that on femora. Tarsi slender (e.g., Fig. 3G), all slightly longer than half length of tibiae; all tarsomeres I–IV
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4. Discussion
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successively shorter posteriorly, and tarsomere V longest. Pretarsal claws simple.
The new genus Cretoleptochromus is placed in the extant Mastigitae on the basis of the geniculate antennae with remarkably long antennomere I, elongate maxillary palps, pointed labial palpomere III, and anteriorly-located eyes (O'Keefe, 2005; Jałoszyński, 2012). Among Mastigitae, Cretoleptochromus can be easily ruled out from Mastigini by lacking spins on scape and pedicel and more or less dilated apical maxillary palpomere. Cretoleptochromus appears to intermingle features belonging to two extant tribes: Clidicini and Leptomastacini. In particular, it shares with Clidicini the following characters: the posterior collar of pronotum distinct, the compound eyes well-developed
ACCEPTED MANUSCRIPT (composed of several dozens of ommatidia), and the antennal flagellomeres (except XI) all elongate. It shares with Leptomastacini the presence of mesocoxal lateroventral bristles. Recent phylogenetic analyses based on adult morphological characters questioned the monophyly of Clidicini because of an alternative placement of Nearctic Papusus as a sister taxon to Leptomastacini + [Clidicus +
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(Palaeoleptochromus + (Euroleptochromus + Leptochromus))] (Jałoszyński, 2012). The unique apomorphy of Papusus and Leptomastacini is the presence of mesocoxal lateroventral bristles (Jałoszyński, 2012), a character also well shown in Cretoleptochromus. Therefore, it is not easy to
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place the new genus in Clidicini or Leptomastacini; we here leave the new genus as incertae sedis within the supertribe Mastigitae. In particular, Cretoleptochromus is separated from Papusus by
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having elongate apical maxillary palpomere, rows of punctures on elytron, and slender tarsi; from Clidicus by elongate maxillary palpomeres III and IV (not enlarged), elongate pronotum, and slender legs; from Leptochromus by its unmodified maxillary palpi with pointed maxillary palpomere IV; from Leptomastax by elongate maxillary palpi with pointed maxillary palpomere IV, short labial
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palpomere III, and slender antennae and legs; and from Ablepton Frivaldszky (Leptomastacini) by well-developed eyes (eyes rudimentary in Ablepton). Among all genera of Mastigitae, the Cretoleptochromus closely resembles the extinct genus
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Palaeoleptochromus from the Late Cretaceous Canadian amber (O’Keefe et al., 1997). They share
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similar body shape with long antennae and legs, unmodified maxillary palpi with pointed maxillary palpomere IV, widely separated antennal insertions, anteriorly-widest pronotum, contiguous procoxae, and widely separated metacoxae. However, Cretoleptochromus differs from Palaeoleptochromus in having a posteriorly-broadened head (narrowing posteriorly in Palaeoleptochromus), more elongate, bullet-shaped maxillary palpomere 4 (shorter and conical in Palaeoleptochromus), and elongate antennal segments (antennomeres VII–X subtriangular in Palaeoleptochromus). Jałoszyński (2012) suggested that the clade [Palaeoleptochromus + (Euroleptochromus + Leptochromus)] is well-supported by four distinguishing characters: 1) the
ACCEPTED MANUSCRIPT presence of postgenal setae; 2) the maxillary palpomere II nearly parallel-sided in distal half; 3) the presence of protrochanteral, and 4) the presence of profemoral bristles. However, only the second character (the maxillary palpomere II nearly parallel-sided in distal half) can be confirmed for Palaeoleptochromus as shown in O’Keefe et al. (1997). More detailed observations of the holotype
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of Palaeoleptochromus schaufussi are needed to confirm the characters mentioned above. In Cretoleptochromus, the postgenal setae appear to be present, although there is no sign of postgenal process (an interesting character found in Palaeoleptochromus and Leptochromus); the maxillary
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palpomere II is nearly parallel-sided in its distal half. It is noteworthy that the protrochanteral and profemoral bristles of Cretoleptochromus are indeed present, but the number of bristles is greatly
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reduced compared to those of the extinct Palaeoleptochromus or the extant Leptochromus. In Cretoleptochromus, there is only one protrochanteral bristle and one profemoral bristle located near the base of profemur. By contrast, there are seven protrochanteral bristles and eight profemoral bristles along the basal half of profemur in Euroleptochromus (Jałoszyński, 2012), and there are one
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protrochanteral bristle and three profemoral bristles in a Palaeoleptochromus species (Leptochromus laselva Lord, Carlton and Leschen; Lord et al., 2014). Jałoszyński (2012) also suggested that Euroleptochromus, Palaeoleptochromus and Leptochromus share highly derived structures on
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postgenae and maxillary palps, probably as part of a specialized feeding or prey capture mechanism.
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The statement is true for Euroleptochromus and Leptochromus as they both possess postgenal process and setal process on maxillary palpomere II, but not for the Cretaceous Palaeoleptochromus. The maxillary palpus of the new genus Cretoleptochromus has no modifications on maxillary palpomere II, which is similar to that of Palaeoleptochromus. The biogeography and mouthpart evolution within Clidicini is tentatively discussed by Jałoszyński (2012), but several specific aspects are still open to question. The new fossil of a slightly older age than that of Palaeoleptochromus may help to clarify this problem. Recently, a new species belonging to the extant genus Clidicus, Clidicus cretaceus, is described
ACCEPTED MANUSCRIPT from the Lower Cretaceous French amber (Kirejtshuk et al., 2015). Kirejtshuk et al. (2015) placed the fossil in Clidicus as supported by distinct longitudinal rows of punctures (on elytron) which are slightly depressed and weakly clavate femora as defined by O’Keefe (2002). However, compared to members of Clidicus, the fossil has much larger eyes that located medially on sides of the head,
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elongate maxillary palpomere III that gradually widened toward apex, and much longer antennae with elongate antennomeres. In Clidicus, the eyes are small, located at anterior part of the head; the apical two maxillary palpomeres are strongly enlarged, and maxillary palpomere III is distinctly
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broader than maxillary palpomere IV. The fossil is definitely not a member of Clidicus; it probably represents a new genus close to Clidicus or the new genus Cretoleptochromus, but more characters
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should be checked to make a more comprehensive comparison, such as postgenal setae, labial palpi, protrochanteral and profemoral bristles, mesocoxal lateroventral bristles, and many other features.
5. Concluding remarks
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The new discovery of a new genus and species of the supertribe Mastigitae from the Upper Cretaceous Burmese amber highlights the palaeodiversity of Mastigitae and even for Scydmaeninae in the Mesozoic. It also represents the oldest fossil record for the supertribe Mastigitae. More
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importantly, the new genus is closely related to the extinct Palaeoleptochromus O'Keefe from the
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Late Cretaceous Canadian amber, bearing significant biogeographic implications for the tribe Clidicini and the supertribe Mastigitae. A comprehensive phylogenetic analysis integrating all extinct (especially Mesozoic fossils) and extant genera of Mastigitae is necessary for understanding the relationships among the Recent three tribes, particularly for Leptomastacini and Clidicini.
Acknowledgements We are grateful to two anonymous reviewers for their helpful comments on the manuscript. The work has been supported by the National Basic Research Program of China (2012CB821903), the
ACCEPTED MANUSCRIPT National Natural Science Foundation of China (J1210006), and the open grant of the Key Laboratory of Economic Stratigraphy and Palaeogeography (2016KF07).
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Jałoszyński, P., 2012. Description of Euroleptochromus gen.n. (Coleoptera, Staphylinidae, Scydmaeninae) from Baltic amber, with discussion of biogeography and mouthpart evolution within Clidicini. Systematic Entomology 37, 346–359.
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Jałoszyński, P., 2014. Phylogeny of a new supertribe Cephenniitae with generic review of Eutheiini
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ACCEPTED MANUSCRIPT Kirejtshuk, A.G., Kurbatov, S.A., Nel, A. 2015. A new species of the genus Clidicus from the Lower Cretaceous of France (Coleoptera: Staphylinidae: Scydmaeninae). Proceedings of the Zoological Institute RAS 319(4), 508–514. Lord, N.P., Carlton, C.E., Leschen, R.A.B., 2014. A new species of Leptochromus Motschulsky
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Scydmaenidae). Systematic Entomology 27, 211–234.
O’Keefe, S.T., Pike, T., Poinar Jr., G., 1997. Palaeoleptochromus schaufussi (gen. nov., sp. nov.), a new antlike stone beetle (Coleoptera: Scydmaenidae) from Canadian Cretaceous Amber. Canadian Entomologist 129, 379–385.
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O'Keefe, S.T., 2005. Scydmaenidae Leach, 1815, in Beutel, R.G., & Leschen, R.A.B., Handbook of Zoology, Coleoptera, Beetles. Vol. 1: Morphology and systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim). De Gruyter, Berlin, New York, pp. 280–288.
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Peris, D., Chatzimanolis, S., Delclòs, X., 2014. Diversity of rove beetles (Coleoptera: Staphylinidae)
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in Early Cretaceous Spanish amber. Cretaceous Research 48, 85–95. Poinar Jr., G., Brown, A.E., 2004. A new subfamily of Cretaceous antlike stone beetles (Coleoptera: Scydmaenidae: Hapsomelinae) with an extra leg segment. Proceedings of the Entomological Society of Washington 106, 789–796. Ross, A.J., Mellish, C., York, P., Crighton, B., 2010. Burmese amber. In: Penney, D. (Ed.), Biodiversity of Fossils in Amber from the Major World Deposits. Siri Scientific Press, Manchester, pp. 208–235. Shi, G., Grimaldi, D.A., Harlow, G.E., Wang, J., Wang, J., Yang, M., Lei, W., Li, Q., Li, X., 2012.
ACCEPTED MANUSCRIPT Age constraint on Burmese amber based on U-Pb dating of zircons. Cretaceous Research 37, 155–163.
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[FIGURE CAPTIONS]
Fig. 1. Photograph of holotype (NIGP163304) of Cretoleptochromus archaicus gen. et sp. nov., in
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Upper Cretaceous amber from northern Myanmar. A. dorsal view; B. ventral view. Scale bars: 1 mm.
Fig. 2. Close-ups of holotype (NIGP163304) of Cretoleptochromus archaicus gen. et sp. nov., under
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normal light. A. head, showing eyes, antennal insertions and labrum; B. ventral view of anterior part of head, showing the left labial palpus and mandibles; C. elytra, showing punctate striae. Scale bars: 200 µm in A and B, 500 µm in C.
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Fig. 3. Close-ups of holotype (NIGP163304) of Cretoleptochromus archaicus gen. et sp. nov., under Zeiss Axio Imager 2 compound microscope using fluorescence as light source. A. dorsal view of head and pronotum; B. ventral view of thorax, showing contiguous procoxae and distinctly separated
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meso- and metacoxae; C. ventral view of anterior part of head, showing setose lacinia and galea; D.
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ventral view of the left maxillary palpus; E. dorsal view of the right maxillary palpus; F. right antenna and part of right maxillary palpus; G. left metatarsus. a, antennomere; e, eye; fcs, fontoclypeal suture; lp, labial palpomere; ma, mandible; mcp, metacoxal plate; mp, maxillary palpomere; Scale bars: 500 µm in A, B and F, 200 µm in others.
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