A new abelisauroid (Dinosauria: Theropoda) from the Huincul Formation (lower Upper Cretaceous, Neuquén Basin) of Patagonia, Argentina

Journal Pre-proof A new abelisauroid (Dinosauria: Theropoda) from the Huincul formation (lower upper Cretaceous, Neuquén Basin) of Patagonia, Argentina Mattia A. Baiano, Rodolfo A. Coria, Andrea Cau PII:

S0195-6671(19)30188-0

DOI:

https://doi.org/10.1016/j.cretres.2020.104408

Reference:

YCRES 104408

To appear in:

Cretaceous Research

Received Date: 16 May 2019 Revised Date:

16 December 2019

Accepted Date: 26 January 2020

Please cite this article as: Baiano, M.A., Coria, R.A., Cau, A., A new abelisauroid (Dinosauria: Theropoda) from the Huincul formation (lower upper Cretaceous, Neuquén Basin) of Patagonia, Argentina, Cretaceous Research, https://doi.org/10.1016/j.cretres.2020.104408. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2020 Elsevier Ltd. All rights reserved.

1

A NEW ABELISAUROID (DINOSAURIA: THEROPODA) FROM THE HUINCUL

2

FORMATION (LOWER UPPER CRETACEOUS, NEUQUÉN BASIN) OF PATAGONIA,

3

ARGENTINA

4 5

Mattia A. Baianoa,b *, Rodolfo A. Coriab, Andrea Cauc.

6 7

a

8

b

9

Plaza Huincul, Neuquén, Argentina.

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CONICET-IIPG, Av. Roca 1242, 8332, General Roca, Río Negro, Argentina. CONICET - Subsecretaría de Cultura de Neuquén - Museo Carmen Funes, Av. Córdoba 55,

c

Geological and Palaeontological Museum ‘Giovanni Capellini’, I-40126 Bologna, Italy.

11 12 13

*Corresponding author.

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Email addresses: [email protected] (M.A. Baiano), [email protected] (R.A. Coria),

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[email protected] (A. Cau)

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Abstract

18

A new ceratosaurian theropod dinosaur, Huinculsaurus montesi gen. et sp. nov., is described

19

here. This taxon is based on the last three dorsal vertebrae and the first and second sacral

20

vertebrae found in association at Aguada Grande, Neuquén Province, Argentina. Although

21

fragmentary, Huinculsaurus shows a unique mix of features which differentiates it from all other

22

theropods, including the sympatric abelisaurid Ilokelesia, and is diagnosed by prezygapophyseal

23

articular facets twice longer than wide, anterior centroparapophyseal lamina strongly developed

24

as an extensive lateral lamina in the posterior dorsal vertebrae, pneumatic foramina located

25

ventrally to the postzygodiapophyseal lamina in the posterior dorsal vertebrae, posteriorly

26

tapering postzygapophysis pointed posteriorly, and an accessory lamina bisecting the

27

parapophyseal centrodiapophyseal fossa in the posterior dorsal neural arches. Phylogenetic

28

analyses recovered Huinculsaurus as most closely related to the Late Jurassic Elaphrosaurus

29

than to other Cretaceous abelisauroids, suggesting the persistence of the elaphrosaurine lineage

30

in South America up to the early Late Cretaceous.

31 32 33

Keywords: Huinculsaurus, Noasauridae, Theropoda, Upper Cretaceous, Patagonia, Argentina.

34 35

1. Introduction Noasauridae is a theropod clade of small to medium-sized forms with a mainly Gondwanan

36

record. Although this taxon was erected almost forty years ago by Bonaparte and Powell (1980),

37

with the description of Noasaurus leali, the current record of this theropod family has remained

38

scarce and is represented by only a handful of forms. The noasaurid record spans from the

39

Middle Jurassic up to the Maastrichtian. The Jurassic forms include the Bathonian-Callovian

40

Spinostropheus gautieri (Sereno et al., 2004; Rauhut & Lopez-Arbarello, 2009), the

41

Kimmeridgian Elaphrosaurus bambergi from Tendaguru, Tanzania (Janensch, 1920; Rauhut &

42

Carrano, 2016) and Limusaurus inextricabilis from the late Oxfordian of China (Xu et al., 2009).

43

The richest noasaurid record comprises Cretaceous forms like the Barremian Ligabueino andesi,

44

Argentina (Bonaparte, 1996), the Albian Genusaurus sisteronis (the so far only known Laurasian

45

noasaurid, Accarie et al., 1995), the Santonian-Campanian Velocisaurus unicus from Argentina

46

(Bonaparte, 1991), the Maastrichtian taxa Noasaurus leali (also from Argentina, Bonaparte and

47

Powell, 1980), Masiakasaurus knopfleri from Magadascar (Sampson et al., 2001),Laevisuchus

48

indicus from India (Huene and Matley, 1933) and a recently described, new noasaurid from the

49

Late Cretaceous of Brazil (Langer et al., 2019). Further Late Cretaceous noasaurids are

50

represented as well by fragmentary material from Argentina, Brazil and Morocco (Agnolin and

51

Martinelli, 2007; Lindoso et al., 2012; McFeeters, 2013; Evans et al., 2015; Brum et al., 2018)

52

and eventually by the controversial Cenomanian Deltadromeus agilis, whether it is confirmed as

53

a basal ceratosaurian (Delcourt, 2017; Delcourt and Iori, 2018), or as a noasaurid (Rauhut and

54

Carrano, 2016; Wang et al., 2017; Delcourt, 2018), instead of as a tetanuran (Sereno et al., 1996;

55

Apesteguía et al., 2016).

56

57

The monophyly of Noasauridae, its placement in Ceratosauria and its internal

58

relationships face the fragmentary nature of most of the included taxa (Carrano et al., 2002;

59

Carrano and Sampson, 2008; Tortosa et al., 2013; Rauhut and Carrano, 2016; Wang et al., 2017;

60

Dal Sasso et al., 2018; Delcourt, 2018). The poor preservation of some taxa of the clade, like

61

Laevisuchus, Noasaurus or Velocisaurus resulted in largely unsolved polytomies among these

62

forms. The recent re-description of Elaphrosaurus bambergi (Rauhut and Carrano, 2016), and

63

the discovery of new ontogenetic stages of Limusaurus (Wang et al., 2017), have increased the

64

information available for a peculiar noasaurid clade, the Elaphrosaurinae (Rauhut and Carrano,

65

2016; Wang et al., 2017).

66

Here we describe a new theropod taxon, Huinculsaurus montesi gen. et sp. nov. (MCF-

67

PVPH-36). It is represented by an immature individual, given that the last three dorsal vertebrae

68

have the neural arches totally separated from the centra (Brochu, 1996). Although fragmentary, it

69

shows a unique suit of characters, allowing the erection of a new noasaurid taxon related to

70

Elaphrosaurus. The presence of a new abelisauroid theropod in the early Late Cretaceous of

71

South America enriches the diversity of Ceratosauria (Baiano et al., 2019), and supports the

72

persistence of Elaphrosaurus-related forms in the last part of the Mesozoic.

73 74

2. Institutional abbreviations

75

MACN-CH, Museo Argentino de Ciencias Naturales, Buenos Aires, Argentina;

76

MAU, Museo Argentino Urquiza, Rincón de los Sauces, Neuquén Province, Argentina;

77

MCF-PVPH, Museo Municipal Carmen Funes, Plaza Huincul, Neuquén Province,

78

Argentina; MEF-PV, Museo Egidio Feruglio, Trelew, Chubut Province, Argentina;

79

MMCH-PV, Museo Museo Municipal “Ernesto Bachmann”, Villa El Chocón, Neuquén

80

Province, Argentina; MPM, Museo Regional Provincial “Padre Manuel Jesús Molina”,

81

Santa Cruz, Argentina.

82 83

3. Materials and methods The identification of the vertebral sequence was based on the description of

84 85

Majungasaurus (O’Connor, 2007) and the re-description of Elaphrosaurus (Rauhut and Carrano,

86

2016). Also, we apply the nomenclature for fossae and laminae proposed by Wilson (1999) and

87

Wilson et al. (2011). The phylogenetic affinities of Huinculsaurus montesi were tested using two

88

independently-developed data sets focusing on non-tetanuran theropods: the data set of Wang et

89

al. (2017), which includes the richest taxon sample for ceratosaurian theropods published so far;

90

and an expanded version of the data set of Dal Sasso et al. (2018), which includes the richest

91

morphological character sample for theropods (see Supplementary Information). The

92

phylogenetic analyses were carried out by using the software TNT, version 1.5 (Goloboff et al.,

93

2008).

94 95 96

3.1. Anatomical abbreviations al, accessory lamina; acdl, anterior centrodiapophyseal lamina; acpl, anterior

97

centroparapophyseal lamina; cpaf, centroparapophyseal fossa; dcpns, caudal process of neural

98

spine; dp, diapophysis; hy, hyposphene; ha, hypantrum; nc, neural canal; ncs, neurocentral

99

suture; ns, neural spine; pacdf, parapophyseal centrodiapophyseal fossa; pcdl, posterior

100

centrodiapophyseal lamina; pcpl, posterior centroparapophyseal lamina; pl, pleurocoel; poz,

101

postzygapophysis; pocdf,postzygapophyseal centrodiapophyseal fossa; podl,

102

postzygodiapophyseal lamina; pp, parapophysis; ppdl, paradiapophyseal lamina; prz,

103

prezygapophysis; prcdf, prezygapophyseal centrodiapophyseal fossa; prdl,

104

prezygodiapophyseal lamina; spol, spinopostzygapophyseal lamina; spof,

105

spinopostzygapophyseal fossa; sprf, spinoprezygapophyseal fossa; sprl, spinoprezygapophyseal

106

lamina; sr, sacral rib; tp, transverse process; 1sc, first sacral centrum; 2sc, second sacral

107

centrum; 1svtp, transverse process of first sacral vertebra; 2svtp, transverse process of second

108

sacral vertebra

109 110

4. Systematic Paleontology

111

Dinosauria Owen, 1842

112

Saurischia Seeley, 1888

113

Theropoda Marsh, 1881

114

Ceratosauria Marsh, 1884

115

Abelisauroidea Bonaparte and Novas, 1985

116

Noasauridae Bonaparte and Powell, 1980

117

Huinculsaurus montesi gen. et sp. nov.

118 119 120

4.1. Derivation of name Huinculsaurus refers to the provenance from the Huincul Formation; and saurus, lizard;

121

montesi, after the late Eduardo Montes, technician from the MCF, who made the final

122

preparation of the holotype specimen and many others relevant specimens of the Vertebrate

123

Paleontology collection of the Carmen Funes museum.

124 125 126 127

4.2. Holotype MCF-PVPH-36 is an immature specimen that includes the articulated sequence of the last three dorsal vertebrae and the first two sacral vertebrae.

128 129

4.3. Diagnosis Huinculsaurus is unique among theropods in showing the following combination of

130

autapomorphic features (marked by *): 1) prezygapophyseal articular facets in posterior dorsal

131

vertebrae twice longer than wide*; 2) anterior centroparapophyseal lamina strongly developed as

132

an extensive lateral lamina in posterior dorsal vertebrae*; 3) pneumatic foramina located

133

ventrally to the postzygodiapophyseal lamina in posterior dorsal vertebrae*; 4) posteriorly

134

tapering postzygapophysis pointed posteriorly*; 5) posterior dorsal neural arches with the

135

parapophyseal centrodiapophyseal fossa separated in two by an accessory lamina (al) (also in

136

Carnotaurus sastrei).

137

Differential diagnosis. Based on the size, degree of neurocentral suture, and morphology

138

of the posterior dorsal vertebrae, the only known specimen of Huinculsaurus montesi differs

139

from the holotype of the sympatric Ilokelesia aguadagrandensis (Coria and Salgado, 1998)

140

because the former represents a smaller and less mature individual. Furthermore, Huinculsaurus

141

montesi differs from Ilokelesia aguadagrandensis based on the presence of long and narrow

142

prezygapophyseal facets in posterior dorsal vertebrae (squared facets in Ilokelesia),

143

dorsomedially-facing prezygapophyseal facets in posterior dorsal vertebrae (dorsolaterally-

144

facing in Ilokelesia), anterior centroparapophyseal lamina which is cranioventrally oriented

145

(subvertical in Ilokelesia), and presence of an accessory lamina crossing the parapophyseal

146

centrodiapophyseal fossa in posterior dorsal vertebrae (lamina absent in Ilokelesia). There is no

147

evidence that these vertebral differences are ontogenetically related in theropods (see Wang et

148

al., 2017), supporting the taxonomic distinction between Huinculsaurus and Ilokelesia.

149 150

4.4. Locality and horizon

The holotype specimen (MCF-PVPH-36) of Huinculsaurus montesi was collected at the

151 152

locality of Aguada Grande, 15 km southern Plaza Huincul City, Neuquén Province, Argentina,

153

about 10 meters north of the holotype specimen of the abelisaurid Ilokelesia aguadagrandensis

154

(Coria and Salgado, 1998) (Fig.1). The fossil-bearing level consists of a medium-sized yellowish

155

sandstone, attributed to the top of the Huincul Formation (upper Cenomanian-Turonian, Keidel,

156

in Wichmann, 1927; Garrido, 2010).

157

4.5. Description

158

The holotype specimen of Huinculsaurus montesi, gen. et sp. nov. consists in a

159 160

continuous sequence of five vertebrae that include the last three presacrals and the first two

161

sacrals. The vertebrae were disarticulated by mechanic preparation in order to gain access to all

162

available information (see Table 1).

163 Specimen

CENL

CRCW

CRCH

CDCW

CDCH

MIDW

MCFPVPH36/01

11.7*

+

+

10.5*

22.4*

+

MCFPVPH36/02

47.5

17.1*

27.6*

32.2*

34.4

MCFPVPH36/03

52.2

31.8*

32.7

37.6

MCFPVPH36/04

50.6

36.2

36.3

MCFPVPH36/05

+

30.2

27*

164 165 166 167 168 169

TOVH NSH

NSL

NSLM

NSW

NSWM IZW

IZL IPPW

IDPW

PP/DP

71.9*

25.7

39.2*

+

16.7

+

17.7

55.3*

60.5

63.9*

0.94

12.7*

89.9

29.2

55.7

42

16.3

5.6

15.5

62.3

46.4*

73.1

0.63

34.7

15.3

80.4*

20.6

46.7

35.7

16.1

5.9

13.1

58.9

50.8

58.4*

0.86

25.8

28.3*

14.6

94

29.2

-

-

10.3

3.2

+

+

-

52.2

-

+

+

+

85*

+

-

-

11.9

5.7

-

-

-

50

-

Principal measurements (mm) of Huinculsaurus montesi, Holotype (MCF-PVPH-36): CDCH, Caudal Centrum Height − maximum height of caudal articular facet; CDCW, Caudal Centrum Width − maximum width of caudal articular facet; CENL, Centrum Length − maximum craniocaudal length; CRCW, Cranial Centrum Width − maximum width of cranial articular facet; CRCH, Cranial Centrum Height − maximum height of cranial articular facet; IDPW, Interdiapophyseal Width – distance between lateral limit of diapophyses; IPPW, Interparapophyseal Width − distance between lateral limit of parapophyses; IZL, Interzygapophyseal Length − distance from cranial

170 171 172 173 174 175 176 177 178 179 180 181 182

margin of right prezygapophysis to caudal margin of right postzygapophysis; IZW, Interzygapophyseal Width − distance between lateral margin of postzygapophyses; MIDW, Midcentral Width − width at central midlength; NSH, Neural Spine Height − dorsoventral extent of neural spine measured from dorsal aspect of postzygapphysis; NSL, Neural Spine Length at the Base − craniocaudal extent of neural spine at spine base (from the cranial margin of spinoprezygapophyseal lamina to caudal margin of postzygapophyses); NSLM, Neural Spine Length at the Mid Height − craniocaudal extent of neural spine at spine midheight; NSW, Neural Spinal Width at the Base − transverse extent of neural spine at spine base; NSWM, Neural Spinal Width at the Mid Height − transverse extent of neural spine at spine midheight; PP/DP, Para-Diapophyseal Index − ratio of interparapophyseal width to diapophyseal width; TOVH, Total Vertebral Height − dorsoventral extent of vertebra including centrum and neural spine; *, incomplete measurement due to missing bone (e.g., partial breakage of a transverse process); +, unable to measure due to damaged/missing bone;—, measurement not applicable for given vertebra.

4.5.1. Eleventh dorsal vertebra (MCF-PVPH-36/01)

183

The centrum is mostly lost, except for a left posterior fragment (Fig. 2A, C, D, E and F).

184

In cranial view (Fig. 2A), the neural canal is oval in shape, higher than wide. The

185

prezygapophyses are preserved only at their bases although they seem to be dorsoventrally

186

extensive. The hypantrum is triangular, and wider ventrally. The parapophyses project far

187

laterally, reaching almost the same amplitude of the transverse processes and are ventrally

188

shifted. The spinoprezygapophyseal fossa (sprf) is deep and narrow, whereas both

189

spinoprezygapophyseal laminae (sprl) are partially incomplete. The ventral process of the

190

prezygapophyses, the anterior centroparapophyseal laminae (acpl) and the prezygodiapophyseal

191

laminae (prdl) delimit a laterally extensive prezygapophyseal centrodiapophyseal fossa (prcdf).

192

The anterior centroparapophyseal lamina is well expanded and ventrally concave in cranial view.

193

The transverse processes are oriented dorsally in an angle of 30°.

194

In lateral view (Fig. 2D, E), the paradiapophyseal lamina (ppdl) connects vertically the

195

parapophyses to the ventral surface of the prezygodiapophyseal laminae. The posterior

196

centroparapophyseal lamina (pcpl) and the centrodiapophyseal lamina seem to emerge together

197

from the suture with the centrum and diverge craniodorsally to connect the parapophysis and the

198

diapophysis, respectively. Thus, these laminae separate the centrodiapophyseal fossa (cdf) in a

199

parapophyseal centrodiapophyseal fossa (pacdf) and a centroparapophyseal fossa (cpaf) (Fig.

200

2F). A small foramen is present between the posterior centroparapophyseal lamina and the

201

posterior centrodiapophyseal lamina (pcdl). The neural spine is partially broken and reduced to a

202

thin sheet of bone with no indication of the presence of any pneumatic cavity at the base. It is

203

dorsoventrally low and has a conspicuous posterior, dorsocaudal projection.

204

In caudal view (Fig. 2B), the anterior and posterior pedicles are slightly laterally

205

projected. The hyposphene is preserved only at its base, and probably was triangular in shape

206

and dorsoventrally high. The postzygapophyses are slightly ventrolaterally oriented, longer than

207

wide and caudally pointed. The postzygapophyseal centrodiapophyseal fossae (pocdf) are wide,

208

deep, and communicate with the inside of the neural arch. A small foramen can be observed on

209

both transverse processes, located ventrally to the postzygodiapophyseal laminae (podl). The

210

spinopostzygapophyseal fossa (spof) is deep and subtriangular, delimited by two

211

spinopostzygapophyseal laminae (spol) that diverge ventrally. In dorsal view (Fig. 2C), the

212

transverse processes have a D-shape outline, due a cranially convex prezygodiapophyseal

213

laminae and a slightly concave postzygodiapophyseal laminae.

214 215 216

4.5.2. Twelfth dorsal vertebra (MCF-PVPH-36/02) The centrum is partially preserved lacking the entire right-side face and part of the cranial

217

articular surface. It shows a spool-like shape and it is longer than high (Fig 3). The left surface

218

lacks pleurocoel, albeit a craniocaudal depression is present just below the neural suture (Fig.

219

3D). The caudal articular surface is concave (Fig. 3B). In the ventral part of the centrum, no mid-

220

keel or mid-groove are present, but several small grooves and crests near the edge of the articular

221

surface probably indicate ligament attachments (Fig. 3F). The craniocaudal length and the

222

dorsoventral height ratio of the cranial articular surface is 1.3 and this value remains constant for

223

the following centra.

224

This vertebra shows an overall morphology of the neural arch, similar to the previous

225

one, although it is larger and the transverse processes are less dorsally inclined. In cranial view

226

(Fig. 3A), the anterior pedicels diverge laterally. The entrance to the neural canal is oval. The

227

rectangular articular facet of the prezygapophyses are dorsomedially oriented and twice longer

228

than wide. The hypantrum is deeper than the preceding vertebra, and furthermore, the

229

prezygapophyses are higher than the craniocaudal length of the articular facets. The medial sides

230

of the prezygapophyses show the contact surfaces for the hyposphene. The

231

spinoprezygapophyseal fossa is deeper and broader than the preceding vertebra. The

232

spinoprezygapophyseal laminae are well-developed although partially broken. The parapophyses

233

project far laterally and are ventrally projected, but to a lesser degree than in the vertebra

234

previously described. The centroparapophyseal lamina and the prezygadiapophyseal lamina are

235

the floor and the roof of a rectangular centrodiapophyseal prezygapophyseal fossa, respectively.

236

In lateral view (Fig. 3D, E), the parapophysis is anteroventrally placed with respect to the

237

diapophysis. The paradiapophyseal lamina still has a significant size, but not to the same degree

238

as in the previous vertebra. A well-developed lamina separates the parapophyseal

239

centrodiapophyseal fossa in two, which is visible only on the right side, because the left side is

240

almost completely broken. There is a fossa placed ventrally to the parapophyseal

241

centrodiapophyseal fossa instead of the foramen present in the same site described with the

242

previous vertebra (Fig. 3E, F). The neural spine shows a caudal rim, gently concave, and a

243

process, dorsocaudally projected, as with the previous vertebra.

244

In caudal view (Fig. 3B), the hyposphene expands ventrally. The postzygapophyses are

245

ventrolaterally oriented, although they appear to be smaller and are less pointed shape, compared

246

to the preceding vertebra. The postzygapophyseal centrodiapophyseal fossae are large and deep.

247

Ventrally to the postzygodiapophyseal laminae there are two foramina, the medial one being the

248

widest. The spinopostzygapophyseal fossa is well developed. It is subtriangular in shape due to

249

the ventral divergence of the spinopostzygapophyseal laminae. The partially broken posterior

250

pedicels diverge laterally.

251

In dorsal view (Fig. 3C), numerous grooves extend mediolaterally on the dorsal surface

252

of the transverse processes, which have the same D-shape of the previous vertebra. These scar-

253

like ridges are also preserved in Majungasaurus (O’ Connor, 2007) and Viavenator (Filippi et

254

al., 2016), which are probably the attachment area for the musculus tendinoarticularis (for

255

crocodiles) or the musculus ascendens thoracicus (for birds) (Organ, 2006).

256 257 258

4.5.3. Thirteenth dorsal vertebra (MCF-PVPH-36/03) This vertebra shows an almost completely preserved neural arch and centrum (Fig. 4).

259

The centrum is amphicoelic and has the same size and spool-like shape observed in the

260

preceding vertebra (Fig. 4E, F). The lateral surfaces lack pleurocoels, although they have well-

261

marked craniocaudal depressions (Fig. 4D, E). Although incomplete, the cranial articular surface

262

has an oval outline, higher than wide (Fig. A). In contrast, the caudal articular surface is circular

263

in shape (Fig. B). Like the previous centrum, in ventral view it bears several small grooves all

264

around the perimeter of the articular surfaces (Fig. 4F).

265

In cranial view (Fig. 4A), the anterior pedicels are sub-parallel. The hypantrum is deep

266

and triangular with its apex dorsally positioned. The contact facets for the hyposphene are well

267

defined. The prezygapophyseal articular facets are craniocaudally long, face dorsomedially and

268

are longer than wide. The dorsoventral height of the prezygapophyses remains greater than the

269

craniocaudal length of the articular facets. The spinoprezygapophyseal fossa is deeper than in the

270

previous vertebrae. The transverse processes are dorsolaterally projected to a lesser degree

271

compared to previous vertebrae.

272

In lateral view (Fig. 4D, E), the parapophysis and diapophysis are located at the same

273

height and form a single structure (pleuropophysis; O’Connor, 2007). The leveling of the

274

parapophysis with the diapophysis results in the absence of laminae and fossae ventral to the

275

transverse process. Only the anterior centrodiapophyseal lamina and the posterior

276

centrodiapophyseal lamina are present, connecting the transverse processes with the pedicels

277

(Fig. 4F). Nevertheless, a perpendicular craniocaudal vestigial crest is visible between these two

278

laminae, separating the surface in two shallow concavities. The neural spine is craniocaudally

279

short as well as dorsoventrally low when compared with the previous vertebrae, and it lacks the

280

caudal process.

281

In caudal view (Fig. 4B), the posterior pedicles are laterally directed. The hyposphene is

282

partially broken, but apparently it was laminar and dorsoventrally longer than in the previous

283

vertebra. The articular facets of the postzygapophyses are partially broken and ventrolaterally

284

oriented. The postzygapophyseal centrodiapophyseal fossae are deep. A small foramen is present

285

cranially to the postzygapophysis.

286 287

In dorsal view (Fig. 4C), the transverse processes taper laterally showing a triangular shape and they are craniocaudally shorter than in the previous vertebrae.

288 289 290

4.5.4. First sacral vertebra (MCF-PVPH-36/04) The centrum has an overall size similar to the preceding vertebrae (Fig. 5B, C). It shows a

291

slightly concave and circular cranial surface although the lateral depressions are shallower (Fig.

292

5A, B and C). The caudal surface is narrower both laterally and dorsoventrally than the cranial

293

one and is partially fused with the second sacral vertebra. Ventrally and near the cranial articular

294

surfaces, there are several grooves and crests (Fig. 5F).

295

In cranial view (Fig. 5A), the entrance to the neural canal is broader than in the previous

296

vertebrae. The hypantrum is triangular, although it is markedly narrower than the anterior

297

vertebrae. The dorsal surfaces of the prezygapophyses are both craniocaudally and laterally

298

short. The prezygapophyseal articular facets are more mediodorsally oriented than in the other

299

vertebrae. The transverse processes maintain a dorsolateral inclination, but less so than in the

300

dorsal vertebrae.

301

In lateral view (Fig. 5B, C), only the anterior centrodiapophyseal lamina (acdl) and the

302

posterior centrodiapophyseal lamina are present. The prezygapophyseal centrodiapophyseal

303

fossa is wider and deeper than in the last dorsal vertebrae. The lateral fossae ventral to the

304

transverse processes are absent, although there is a shallow fossa on the junction between the

305

neural arch and the centrum. The transverse processes are robust. The neural spine is fused with

306

the neural spine of next vertebra.

307

In caudal view, the neural arch is partially preserved and fused to the second sacral

308

vertebra. The only visible parts are the right postzygodiapophyseal lamina, the posterior part of

309

the right transverse process and the right postzygapophyseal centrodiapophyseal fossa. Both

310

laminae and fossae are reduced with respect to the dorsal vertebrae.

311

In dorsal view (Fig. 5E), the transverse processes are laterally and craniocaudally short.

312

Unlike the previous dorsal vertebrae, the transverse processes are rectangular. The neural spine is

313

fused with the second sacral vertebra and maintains the same dorsoventral height of the last

314

dorsal vertebra. It lacks the mediolateral expansion of the dorsal part of the neural spine.

315 316 317 318

4.5.5. Second sacral vertebra (MCF-PVPH-36/05) The centrum is very incomplete and shows a dorsoventrally low anterior articular surface. Only the left portion of the cranial surface of the centrum is preserved, which is fused to the

319

centrum of the preceding vertebra (Fig. 5C). In caudal view, both the neural arch and centrum

320

are poorly preserved (Fig. 5D).

321

The neural arch of second sacral vertebra is incomplete (Fig. 5B, C). The transverse

322

processes have a similar morphology and lateral extension of sacral 1, and preserve a slight

323

dorsolateral inclination (Fig. 5D, E). Given that the sacral vertebra is badly preserved, it is not

324

possible to estimate the amount of pneumaticity of the sacral complex. However, it shows no

325

indication of pneumaticity dorsal to the transverse processes.

326

On the right side (Fig. 5C), a portion of the sacral rib is fused to the transverse process

327

showing a cranially located transverse process/rib complex. In dorsal view (Fig. 5E), the

328

transverse processes project laterally, as in the first sacral vertebra. The neural spine is preserved

329

only in its anterior part, which is fused with the previous neural spine and it is dorsoventrally

330

low. Like the first sacral vertebra, it lacks the mediolateral expansion of the dorsal part of the

331

neural spine.

332 333 334

5. Comparation with others theropods The combination of very narrow prezygapophyses articular facets (twice longer than

335

wide), and prezygapophyses higher than the craniocaudal length of the articular facets (bearing a

336

ventral process) is observed exclusively in Huinculsaurus among known theropods.

337

Interestingly, long articular facets of the prezygapophyses are also present in Herrerasaurus

338

(Novas, 1994), Eoabelisaurus (Pol and Rauhut, 2012; MEF-PV-3990), Masiakasaurus (Carrano

339

et al., 2002), and Dahalokely (Farke and Sertich, 2013) (Fig. 6A, D), and differ from the rather

340

squared prezygapophyses articular facets of Ilokelesia (Coria and Salgado, 1998), Carnotaurus

341

(Bonaparte et al., 1990), Majungasaurus (O’Connor 2007) and Skorpiovenator (MMCH-PV 48)

342

(Fig. 6B, C). On the other hand, among abelisauroids (although not exclusively), dorsoventrally

343

high prezygapophyses with a ventral process are also present in Dahalokely (Farke and Sertich,

344

2013), Carnotaurus (Bonaparte et al., 1990), Ilokelesia (Coria and Salgado, 1998) and

345

Skorpiovenator (MMCH-PV 48) (Fig. 6E, F and G), and absent in Elaphrosaurus (Fig. 6H).

346

Plesiomorphically, the prezygapophyseal articular facets of Huinculsaurus face dorsomedially,

347

as in Eoabelisaurus (MEF-PV-3990), Ceratosaurus, Sinraptor and Allosaurus (Madsen, 1976;

348

Currie and Zhao, 1993; Madsen and Welles, 2000), unlike the dorsolaterally faced articular

349

facets present in most abelisauroids (like Masiakasaurus, Majungasaurus, Ilokelesia,

350

Skorpiovenator and Carnotaurus) (Bonaparte et al., 1990; Coria and Salgado, 1998; Carrano et

351

al., 2002; O’Connor 2007; Canale et al., 2009).

352

The posterior dorsal neural spines of Huinculsaurus are lower and narrower than in

353

abelisaurids. A similar morphology is observed in several basal neotheropods, including

354

Dilophosaurus (Welles, 1984) and Elaphrosaurus (Rauhut and Carrano, 2016). Huinculsaurus

355

shows a poorly developed dorsocaudal process of the neural spine (dcpns), as in Dilophosaurus,

356

Dahalokely (Welles, 1984; Farke and Sertich, 2013) and Skorpiovenator (MMCH-PV 48), but

357

unlike the well-developed condition of Viavenator (Filippi et al., 2016).

358

Huinculsaurus lacks the dorsocranial process of the neural spines present in the dorsal

359

vertebrae of Dahalokely and Viavenator (Farke and Sertich, 2013; Filippi et al., 2016, 2017). The

360

peculiar D-shape of the dorsal view of the transverse processes of Huinculsaurus is also present

361

in the posterior dorsals of most abelisauroids like Dahalokely, Carnotaurus, Majungasaurus,

362

Masiakasaurus, Eoabelisaurus (MEF-PV-3990), Skorpiovenator (MMCH-PV 48) and Ilokelesia

363

(Bonaparte et al., 1990; Coria and Salgado, 1998; O’Connor, 2007; Carrano et al., 2011; Farke

364

and Sertich, 2013), which differs from the triangular shape observed in Elaphrosaurus (Rauhut

365

and Carrano, 2016) and various basal neotheropods (e.g, Raath, 1977; You et al., 2014) or the

366

rectangular shape seen in tetanurans (e.g. Brochu, 2003; Coria and Currie, 2016). As in other

367

abelisauroids, except Carnotaurus (Bonaparte et al., 1990), Huinculsaurus does not show

368

transverse processes that are cranially oriented. Like in other abelisauroids, the parapophyses are

369

far laterally projected from the neural arch, being as extended as the diapophyses. However, as in

370

Carnotaurus, Dahalokely, Majungasaurus and Viavenator (Bonaparte et al., 1990; O’Connor,

371

2007; Farke and Sertich, 2013; Filippi et al., 2016, 2017), in Huinculsaurus the parapophyses are

372

also anterolaterally projected and visible beneath the transverse processes in dorsal view. The

373

well-developed lateral wing-like anterior centroparapophyseal lamina is only present in

374

Huinculsaurus, and represents a diagnostic feature of this taxon.

375

The posterior centroparapophyseal lamina is well-developed and sub-horizontal as in

376

Carnotaurus, Majungasaurus and Viavenator (Bonaparte et al., 1990; O’Connor, 2007; Filippi et

377

al., 2016, 2017). In contrast, in Skorpiovenator (MMCH-PV 48), this lamina is oriented

378

caudoventrally, and in Eoabelisaurus (MEF-PV-3990) it is not developed as a distinct lamina,

379

but as a low crest. The anterior centroparapophyseal lamina is cranioventrally oriented as in

380

Eoabelisaurus (MEF-PV-3990), Majungasaurus and Masiakasaurus (O’Connor, 2007; Carrano

381

et al., 2011), unlike the subvertical oriented laminae present in Skorpiovenator (MMCH-PV 48),

382

Ilokelesia and Carnotaurus (Bonaparte et al., 1990; Coria and Salgado, 1998). The presence of a

383

lamina that separates the parapophyseal centrodiapophyseal fossa in two fossae is present also in

384

Carnotaurus (Bonaparte et al., 1990), but is absent in other abelisauroids.

385

The concave postzygodiapophyseal lamina is present in Eoabelisaurus (MEF-PV-3990),

386

Skorpiovenator (MMCH-PV 48), Majungasaurus, and Viavenator (O’Connor, 2007; Filippi et

387

al., 2016). In Dahalokely (Farke and Sertich, 2013), Carnotaurus (Bonaparte et al., 1990) and

388

Masiakasaurus (Carrano et al., 2011), this lamina is nearly straight. Furthermore, the presence of

389

foramina lateral to the postzygapophyseal centrodiapophyseal fossa and ventral to the

390

postzygadiapophyseal lamina is a distinctive character of Huinculsaurus.

391

The new taxon shows the postzygapophysis of posterior vertebrae longer than wide, as in

392

Eoabelisaurus (MEF-PV-3990) and Elaphrosaurus (Rauhut and Carrano, 2016), but unlike

393

Dahalokely (Farke and Sertich, 2013), Masiakasaurus (Carrano et al., 2002) and members of

394

Abelisauridae. In Huinculsaurus, the hyposphene is proportionally more developed

395

dorsoventrally than in Elaphrosaurus, Majungasaurus and Masiakasaurus (O’Connor, 2007;

396

Carrano et al., 2011; Rauhut and Carrano, 2016). The inverted cone-shape of the hyposphene can

397

also be seen in Eoabelisaurus (MEF-PV-3990), Elaphrosaurus, Dahalokely, Viavenator,

398

Carnotaurus, Sinraptor, Condorraptor , though it is less discernible in Tyrannosaurus

399

(Bonaparte et al., 1990; Currie and Zhao, 1993; Brochu, 2003; Rauhut, 2005; Farke and Sertich,

400

2013; Filippi et al., 2016; Rauhut and Carrano, 2016). The neural canal of Huinculsaurus is oval,

401

as in Eoabelisaurus (MEF-PV-3990), unlike the circular-shaped neural canal of Carnotaurus

402

(Bonaparte et al., 1990). As in other abelisauroids, the parapophyses of the last dorsal vertebrae

403

are dorsally shifted and fused to the prezygodiapophyseal laminae, forming a single structure

404

with the diapophyses (O’Connor, 2007). However, the migration of the parapophysis in the

405

prezygodiapophyseal lamina is abrupt in Huinculsaurus, lacking the intermediate position seen

406

in Eoabelisaurus (MEF-PV-3990), Carnotaurus and Majungasaurus (Bonaparte et al., 1990;

407

O’Connor, 2007). The new taxon differs from the aforementioned taxa, in which the

408

parapophysis of the twelfth dorsal neural arch is nearly at the same position as the diapophysis:

409

this condition results in the reduction of the paradiapophyseal lamina and the loss of posterior

410

centroparapophyseal lamina, with consequently no separation of the centrodiapophyseal fossa

411

into two separate fossae.

412

The triangular transverse processes observed in the dorsal view of the last dorsal vertebra

413

are also present in Majungasaurus (O’Connor, 2007) and, to a lesser degree, in Eoabelisaurus

414

(MEF-PV-3990), which differ from the rectangular transverse processes of Carnotaurus

415

(Bonaparte et al., 1990). As in Carnotaurus (Bonaparte et al., 1990), Majungasaurus (O’Connor,

416

2007) and Rahiolisaurus (Novas et al., 2010), the last dorsal vertebra is incorporated into the

417

sacrum, contacting the ilia laterally. The reduction of the lateral width of the sacral centra in

418

Huinculsaurus is also present in Skorpioventor (MMCH-PV 48), Carnotaurus, the sacrum

419

referred to Kryptops (but likely belonging to a tetanuran, see Wang et al., 2017), Rajasaurus, and

420

Rahiolisaurus (Bonaparte et al., 1990; Wilson et al., 2003; Sereno and Brusatte, 2008; Novas et

421

al., 2010). Huinculsaurus resembles other abelisauroids in the curvature of ventral margin of

422

sacral vertebrae, which is different from the straight ventral margin of Rajasaurus and

423

Rahiolisaurus (Wilson et al., 2003; Novas et al., 2010).

424

The ratio between the craniocaudal length of the centrum and the dorsoventral height of

425

the cranial surface of the centrum of Huinculsaurus is ~1.3, an intermediate value between those

426

in the noasaurids, Masiakasaurus and Elaphrosaurus (ratio ≥1.5), and other abelisauroids where

427

the ratio is near to 1. The lack of lateral pneumatic foramina on the dorsal centra present in

428

Huinculsaurus is also a condition present in Masiakasaurus (Carrano et al., 2011),

429

Majungasaurus (O’Connor, 2007), Rahiolisaurus (Novas et al., 2010), in the posterior dorsal

430

centra of Eoabelisaurus (MEF-PV-3990), in Dahalokely (Farke and Sertich, 2013), and in the

431

only known dorsal vertebra of Ilokelesia (Coria and Salgado, 1998). This condition is unlike the

432

presence of one or two pleurocoels in Skorpiovenator (MMCH-PV 48), Ekrixinatosaurus,

433

Carnotaurus and Viavenator (Bonaparte et al., 1990; Calvo et al., 2004; Filippi et al., 2016).

434

However, we cannot rule out that the absence of pneumatic centra in MCF-PVPH-36 is related to

435

the inferred immaturity of the specimen. All known centra of Huinculsaurus lack ventral grooves

436

or medial keels as in Eoabelisaurus (MEF-PV-3990) and Skorpiovenator (MMCH-PV 48).

437 438

6. Phylogenetic analyses

439

To investigate the phylogenetic relationships of Huinculsaurus montesi, we used two

440

large data matrices focusing on basal theropods (Wang et al., 2017; Dal Sasso et al., 2018). The

441

character matrices were analyzed using the software TNT version 1.5 (Goloboff, Farris and

442

Nixon, 2008). For each data set, we performed 100 replications of the “New Technology” search

443

analysis, using default parameters. Subsequently, the most parsimonious trees (MPTs) resulting

444

from the primary search were subjected to a second TBR branch swapping round. In both data

445

matrices, character states present in Huinculsaurus that may be related to the immaturity of the

446

specimen were conservatively scored as “unknown”.

447 448

Wang et al. (2017) data set

449

We added two new morphological characters (characters 745 and 746, see Suppl. Inf.),

450

and re-scored the character 399 as 1 for Elaphrosaurus and Dahalokely (see Suppl. Inf.). Since

451

the purpose of this work is to describe the phylogenetic relationship of Huinculsaurus, we

452

excluded a priori all Limusaurus OTUs except for the “L. inextricabilis composite coding”,

453

because it is the OTU with highest number of subadult/adult scored characters. We added two

454

new operational taxonomic units, one based on Huinculsaurus, and one for the taxon Afromimus

455

tenerensis based on the description of Sereno (2017). The updated data matrix includes 746

456

characters and 200 operational taxonomic units.

457 458

Dal Sasso et al. (2018) dataset

459

We added nine new operational taxonomic units, including Huinculsaurus, in order to

460

sample more accurately among abelisauroids (see Suppl. Inf.). We also added two

461

ornithomimosaurs to the coelurosaurian sample (i.e., Nqwebasaurus and Gallimimus), to test the

462

alternative hypotheses on the affinities of Afromimus. The updated data matrix includes 1781

463

characters and 96 operational taxonomic units.

464 465

7. Results and Discussion

466

Sereno (2017) described a fragmentary theropod from the Lower Cretaceous of

467

Niger, and referred it to a new ornithomimosaurian coelurosaur, Afromimus tenerensis,

468

which we consider here as a noasaurid (as also recently discussed by Cerroni et al., 2019),

469

due to the lack of unambiguous ornithomimosaurian synapomorphies (Makovicky et al.,

470

2004). In particular, Sereno (2017) listed some features in the caudal vertebrae and in the

471

pedal ungual shared by Afromimus and ornithomimosaurs and dismissed the referral to

472

Abelisauroidea. We note that the features listed by Sereno (2017) in support of an

473

ornithomimosaurian status for Afromimus are also present in Elaphrosaurus (Rauhut and

474

Carrano, 2016) and Masiakasaurus (Carrano et al., 2002). Furthermore, the morphology of

475

the tibia and fibula is comparable to non-tetanuran neotheropods because of its proximally

476

placed short fibular crest, confluent with the condylar region, its mediolaterally narrow

477

facet for the ascending process of the astragalus, and its broad-based distal end of the fibula

478

which broadly overlaps the tibia (Carrano et al., 2002; Rauhut, 2003). On the contrary, the

479

specimen shares several derived features with ceratosaurians and with noasaurids in

480

particular, including a fused astragalus-calcaneum, a broad fibular proximal fossa that is

481

oriented posteromedially and is bound by a marked lip, and a prominent attachment scar for

482

the m. iliofibularis (Carrano et al., 2002; Carrano and Sampson, 2008; Tortosa et al., 2013;

483

Rauhut and Carrano, 2016).

484 485

The first phylogenetic analysis recovered over 50000 MPTs with a tree length of 4496 steps (consistence index, CI: 0.2046; retention index, RI: 0.6385). The strict

486

consensus of all of the shortest trees found (Fig. 7A; Supp. Inf. 3) places Huinculsaurus as

487

the sister taxon of Elaphrosaurus, clearly nested within Noasauridae. Huinculsaurus shares

488

with Elaphrosaurus the presence of posterior dorsal vertebrae with anteroposteriorly

489

expanded neural spines with fan-shaped distal ends (character 399, also present in

490

Dahalokely and some maniraptorans); and mediolaterally narrower transverse dimensions

491

of mid-sacral centra relative to other sacral centra (character 414). Afromimus is recovered

492

among noasaurids, and is not related to ornithomimosaurian coelurosaurs.

493

The second phylogenetic analysis recovered 1440 MPTs with a tree length of 4622 steps

494

(consistence index, CI: 0.2934; retention index, RI: 0.5256). The strict consensus of all of the

495

shortest trees found (Fig. 7B; Supp. Inf. 3) places Huinculsaurus as the sister taxon of

496

Elaphrosaurus, and this clade is part of a series of noasaurid-grade lineages which form a

497

paraphyletic series leading to Abelisauridae. In all of the shortest trees found, Afromimus is

498

found among abelisauroids and is not related to ornithomimosaurian coelurosaurs.

499

The two data sets were developed independently, and included different character and

500

taxon samples, which only partially overlap. It is beyond the aim of this study to discuss the

501

differences between the topologies of Ceratosauria recovered by the two alternative data sets:

502

nevertheless, it is noteworthy that both analyses support Huinculsaurus as a non-abelisaurid

503

abelisauroid (“noasaur-grade” abelisauroids), closely related to Elaphrosaurus.

504

Huinculsaurus shares with some noasaurids the presence of posterior dorsal vertebrae

505

much longer than high (also present in Eoraptor and some basal theropods; unknown in

506

Deltadromeus, Genusaurus, Velocisaurus and Noasaurus). The conspicuous ventral process on

507

the prezygapophyses is present in Huinculsaurus and some abelisaurids like Ilokelesia,

508

Carnotaurus and Majungasaurus, whereas the presence of far laterally projected parapophyses

509

in posterior trunk vertebrae is an abelisauroid feature present in some noasaurids and abelisaurids

510

(also present in some basal tetanurans). Finally, Huinculsaurus differs from other noasaurids like

511

Limusaurus, Elaphrosaurus and Masiakasaurus in the presence of posterior dorsal neural spines

512

broadly rectangular, and approximately as dorsoventrally high as anteroposteriorly long (also

513

present in several basal theropods and some maniraptorans). Huinculsaurus is part of one of the richest terrestrial associations of fossil vertebrates

514 515

known from Northern Patagonia preserved in the hard sandstones of the Huincul Formation

516

(Cenomanian-Turonian). This unit has also yielded remains of the abelisaurids Ilokelesia

517

aguadagrandensis (Coria and Salgado, 1998) and Skorpiovenator bustingorryi (Canale et al.,

518

2009), the carcharodontosaurids Mapusaurus rosae (Coria and Curie, 2006) and Taurovenator

519

violantei (Motta et al., 2016), the megaraptoran Aoniraptor libertatem (Motta et al., 2016), the

520

tetanuran Gualicho shinyae (Apesteguía et al., 2016), and fragmentary material assigned to

521

different less inclusive theropod taxa (Motta et al., 2016). The dinosaur record of the formation

522

includes sauropods such as the rebbachisaurid Cathartesaura anaerobica (Gallina and

523

Apesteguía, 2005), and the titanosaurs Argentinosaurus huinculensis (Bonaparte and Coria,

524

1993) and Choconsaurus baileywillisi (Simón et al., 2017). The fossil record comprises also

525

turtle plates, crocodiles and lungfish teeth, as in Ameghinoceratodus iheringi (Apesteguía et al.,

526

2007).

527

Besides some putative noasaurid-like teeth described for the Cenomanian of Brazil

528

(Lindoso et al., 2012), Huinculsaurus helps in filling the Barremian-Santonian gap that existed in

529

the South American noasaurid record (Fig. 8).

530

The complete lack of fusion between dorsal centra and neural arches of Huinculsaurus

531

suggests an early ontogenetic stage of the specimen. Thus, presumably the individual was

532

considerably far from reaching its maximum adult size. Yet, the absolute sizes of the vertebral

533

elements are comparable with other noasaurids. In addition, the phylogenetic relationships of

534

Huinculsaurus depict it as possibly first Cretaceous elaphrosaurine (Fig. 7), although such

535

hypothesis is considered as tentative due to the relatively poor completeness of this specimen.

536

Elaphrosaurinae is a clade of Jurassic abelisauroids characterized by several features convergent

537

with the ornithomimosaurian coelurosaurs, including loss of the dentition, a relatively gracile-

538

built axial skeleton and elongate distal hindlimbs elements, suggesting cursorial adaptations (Xu

539

et al., 2009; Rauhut and Carrano, 2016; Wang et al., 2017). Even ignoring the relationships with

540

elaphrosaurines, the unique combination of features in Huinculsaurus supports the presence of a

541

“basal” abelisauroid in the Huincul Formation, distinct from the abelisaurids, which leads us to

542

consider that Cenomanian-Turonian South American ceratosaurians were more diverse and

543

successful than previously thought.

544

The re-evaluation of Afromimus as an abelisauroid, instead of as an ornithomimosaurian,

545

and the possible persistence of the “ornithomimosaur-mimic” elaphrosaurines up to the mid-

546

Cretaceous of Patagonia, suggest that during most of the Cretaceous, several lineages of small-

547

bodied and long-legged abelisauroids occupied, in Western Gondwana, those ecological roles

548

represented by the maniraptoriform coelurosaurs during the same interval in the Northern

549

Hemisphere (Rauhut, 2003). The persistence and abundance of these small abelisauroids in the

550

Southern Hemisphere, and their possible ecological overlap with the coelurosaurs, may thus

551

explain the paucity of non-paravian maniraptoriforms in the rich faunal assemblages from the

552

Cretaceous of Africa and South America (Agnolin and Martinelli, 2007; Motta et al., 2016;

553

Baiano et al., 2019).

554 555 556 557

8. Conclusions We described a new theropod dinosaur, Huinculsaurus montesi gen. et sp. nov., based on an articulated series of vertebrae from the Aguada Grande locality of the Neuquén Province,

558

Argentina. Although based on a very fragmentary specimen, H. montesi differs from the other

559

known theropods due to a unique combination of features, and it results phylogenetically more

560

closely related to the Jurassic abelisauroid Elaphrosaurus than to other Cretaceous taxa. We also

561

tested, for the first time using numerical analyses, the affinities of the African theropod

562

Afromimus, and showed that it is more parsimoniously referable to Abelisauroidea instead of to

563

Ornithomimosauria. The presence of several lineages of small-bodied abelisauroids and the

564

persistence of the elaphrosaurines in the mid-Cretaceous of Africa and South America may

565

explain the relative paucity of coelurosaurians in the Southern Continents compared to the richer

566

Laurasian record of ornithomimosaurs and maniraptorans.

567 568

Nomenclatural act

569

The electronic version of this article in portable document format will represent a

570

published work according to the ICZN, and hence the new names contained in the

571

electronic version are effectively published under that Code from the electronic edition

572

alone. This published work and the nomenclatural acts it contains have been registered

573

in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs

574

(Life Science Identifiers) can be resolved and the associated information viewed through

575

any standard web browser by appending the LSID to the prefix http://zoobank.org/.

576

New Species Registration

577

The following information was supplied regarding the registration of a newly described

578

species:

579

Publication LSID: urn:lsid:zoobank.org:pub:607412D6-1CA9-40EF-B803-D5FD3C3305CE

580

Genus name, Huinculsaurus Baiano, Coria and Cau LSID: urn:lsid:zoobank.org:act:2755F487-

581

AD8A-48A0-A16B-4971493F2511

582

Species name, Huinculsaurus montesi Baiano, Coria and Cau LSID:

583

urn:lsid:zoobank.org:act:E037247D-8C7E-4FCE-BD3E-0BB705ABB2DF

584 585

ACKNOWLEDGMENTS

586

The specimen MCF-PVPH-36 was first prepared by one of the authors (RAC) and

587

finished by E. Montes (MCF). We thank M. Ezcurra and A. Kramarz (MACN), L. Filippi

588

(MAU), D. Pol and J. Carballido (MEF), and J. Canale (MMCH-PV) for giving access to

589

the specimens under their care. D. Pol and J. Carballido made useful comments on an early

590

stage of the manuscript. We thank to J. Canale and another anonymous reviewer for their

591

comments, which greatly improved the manuscript, and to E. Koutsoukos (CR Editor-in-

592

Chief) for his permanent assistance. K. Kamra for English editing. To the Museo Municipal

593

Carmen Funes and Municipalidad de Plaza Huincul for technical and logistical support.

594 595

References

596

Accarie, H., Beaudoin, B., Dejax, J., Fries, G., Michard, J. G., and Taquet, P. (1995). Découverte

597

d'un dinosaure théropode nouveau (Genusaurus sisteronis ng, n. sp.) dans l'Albien marin de

598

Sisteron (Alpes de Haute-Provence, France) et extension au Crétacé inférieur de la lignée

599

cératosaurienne. Comptes rendus de l'Académie des sciences. Série 2. Sciences de la terre et des

600

planètes, 320, 327-334.

601 602

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Figure captions

874 875

Figure 1. Location map of fossil site. A, Map of Argentina and Neuquén Province. B, locality of

876

Huinculsaurus montesi, Holotype, MCF-PVPH-36 quarry (yellow mark).

877 878

Figure 2. Huinculsaurus montesi, Holotype, MCF-PVPH-36/01. (A,C-F) Caudal-most portion of

879

eleventh dorsal centrum and (A-F) eleventh dorsal neural arch in anterior (A), posterior (B),

880

dorsal (C), left lateral (D), right lateral (E), and ventral (F) views. Scale bar: 10 mm.

881 882

Figure 3. Huinculsaurus montesi, Holotype, MCF-PVPH-36/02. (B-F) Twelfth dorsal centrum

883

and twelfth dorsal neural arch in anterior (A), posterior (B), dorsal (C), left lateral (D), right

884

lateral (E), and ventral (F) views. Scale bar: 10 mm.

885

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Figure 4. Huinculsaurus montesi, Holotype, MCF-PVPH-36/03.(A-F) Thirteenth dorsal centrum

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and neural arch in anterior (A), posterior (B), dorsal (C), left lateral (D), right lateral (E), and

888

ventral (F) views. Scale bar: 10 mm.

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Figure 5. Huinculsaurus montesi, Holotype, MCF-PVPH-36/04-05. First and second sacral

891

vertebrae in anterior (A), left lateral (B), right lateral (C), posterior (D), dorsal (E), and ventral

892

(F) views. Scale bar: 10 mm.

893 894

Figure 6. Comparisons of posterior dorsal vertebrae of Huinculsaurus (A, E), Ilokelesia (B, F),

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Carnotaurus (C, G), Masiakasaurus (D) and Elaphrosaurus (H) in dorsal (A-D) and lateral (E-

896

H) views, depicting the states of characters 745 and 746 (see Suppl. Inf.). (B and F, MCF-PVPH-

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35; MACN-CH-894; D, modified from Carrano et al., 2002; H, modified from Rauhut and

898

Carrano, 2016). Not to scale.

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Figure 7. Ceratosaurian affinities of Huinculsaurus. A) Strict Consensus of over 50,000 MPTs

901

based on the data set of Wang et al. (2017). B) Reduced Strict Consensus of 1440 MPTs based

902

on the data set of Dal Sasso et al. (2018). In B), four “wild card” taxa were pruned a posteriori to

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improve resolution among the other taxa: Afromimus, Berberosaurus (both placed among non-

904

abelisaurid ceratosaurians), Pampadromaeus (placed among sauropodomorphs) and Sarcosaurus

905

woodi (placed among basal theropods). In both diagrams, relationships among tetanurans

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collapsed for brevity.

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Figure 8. Stratigraphically calibrated cladogram of the Noasauridae based on the results of the

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first phylogenetic analysis.

Highlights A new abelisauroid theropod Huinculsaurus is described. Huinculsaurus fills the Barremian-Santonian gap of noasaurids record. Elaphrosaurine lineage survived in South America up to the early Upper Cretaceous.

Credit Author Statement Mattia Antonio Baiano: Writing - Original Draft, Writing - Review & Editing Rodolfo Anibal Coria: Writing - Original Draft, Writing - Review & Editing, Resources Andrea Cau: Writing - Original Draft, Writing - Review & Editing

Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: