[Paleontology • 2024] Koleken inakayali • A New abelisaurid Dinosaur from the end Cretaceous of Patagonia and Evolutionary Rates among the Ceratosauria

 

Koleken inakayali 

 Pol,  Baiano, Černý, Novas, Cerda & Pittman, 2024

 

DOI: 10.1111/cla.12583

Abstract

Gondwanan dinosaur faunae during the 20 Myr preceding the Cretaceous–Palaeogene (K/Pg) extinction included several lineages that were absent or poorly represented in Laurasian landmasses. Among these, the South American fossil record contains diverse abelisaurids, arguably the most successful groups of carnivorous dinosaurs from Gondwana in the Cretaceous, reaching their highest diversity towards the end of this period. Here we describe Koleken inakayali gen. et sp. n., a new abelisaurid from the La Colonia Formation (Maastrichtian, Upper Cretaceous) of Patagonia. Koleken inakayali is known from several skull bones, an almost complete dorsal series, complete sacrum, several caudal vertebrae, pelvic girdle and almost complete hind limbs. The new abelisaurid shows a unique set of features in the skull and several anatomical differences from Carnotaurus sastrei (the only other abelisaurid known from the La Colonia Formation). Koleken inakayali is retrieved as a brachyrostran abelisaurid, clustered with other South American abelisaurids from the latest Cretaceous (Campanian–Maastrichtian), such as Aucasaurus, Niebla and Carnotaurus. Leveraging our phylogeny estimates, we explore rates of morphological evolution across ceratosaurian lineages, finding them to be particularly high for elaphrosaurine noasaurids and around the base of Abelisauridae, before the Early Cretaceous radiation of the latter clade. The Noasauridae and their sister clade show contrasting patterns of morphological evolution, with noasaurids undergoing an early phase of accelerated evolution of the axial and hind limb skeleton in the Jurassic, and the abelisaurids exhibiting sustained high rates of cranial evolution during the Early Cretaceous. These results provide much needed context for the evolutionary dynamics of ceratosaurian theropods, contributing to broader understanding of macroevolutionary patterns across dinosaurs.

DINOSAURIA Owen, 1842.

THEROPODA Marsh, 1881.

CERATOSAURIA Marsh, 1884.

ABELISAURIDAE Bonaparte and Novas, 1985

BRACHYROSTRA Canale et al., 2009

FURILEUSAURIA Filippi et al., 2016

Koleken gen. n. 

Derivation of name: Adapted from Kóleken, a name in Teushen language spoken by the native population of central Patagonia that means “coming from clay and water”, given the specimen was found in a sedimentary section dominated by claystone representing an estuarine environment.

Koleken inakayali gen. et sp. n.

Derivation of name: Honouring Inakayal, one of the last chiefs of Tehuelches, native people from central Patagonia. He is known for his resistance against Argentina's Conquest of the Desert military campaign, which resulted in the decimation and displacement of native communities from Patagonia. After his capture and eventual death in 1888, Inakayal's skeleton was stored at the La Plata Museum Anthropology collection but in 1994 his skeleton was respectfully restituted in its native place and buried by his people near the town of Tecka, in central Patagonia (Chubut Province, Argentina).

Holotype: MPEF-PV 10826. The specimen includes closely associated (but disarticulated) remains of the skull and atlas, as well as the articulated postcranial skeleton composed of the posteriormost eight dorsal vertebrae, a complete sacrum, eight caudal vertebrae, an almost complete pelvis and hind limbs. Select measurements are provided in Table S1.

Locality and horizon: The specimen was found at the Cerro Bayo Norte area, east of the Sierra de La Colonia, centre north of Chubut Province, Argentina (Fig. 1). Precise geographical provenance is deposited at the MPEF collection. The specimen was found close to the base of the stratigraphic section of the La Colonia Formation that crops out in this region (see Gasparini et al., 2015: Fig. 2). The age of the base of this unit has been recently restricted to the early Maastrichtian (Clyde et al., 2021), constraining the age of the new taxon to the Maastrichtian.

Diagnosis: Koleken inakayali is a brachyrostran abelisaurid different from other theropods in having the following set of autapomorphies (marked with a *): (i) medially smooth paradental plates; (ii) dorsal surface of the nasal with a row of foramina orientated obliquely with respect to the longitudinal skull axis; (iii) *anterior ramus of the postorbital lacking the lateral wall reflected by a dorsoventral height less than half of its anteroposterior length, which makes the orbital surface face ventrally instead ventromedially; (iv) *dorsal surface of the postorbital with a ...

Diego Pol, Mattia Antonio Baiano, David Černý, Fernando E. Novas, Ignacio A. Cerda and Michael Pittman. 2024. A New abelisaurid Dinosaur from the end Cretaceous of Patagonia and Evolutionary Rates among the Ceratosauria. Cladistics. DOI: 10.1111/cla.12583

[Paleontology • 2020] Tralkasaurus cuyi • A New Abelisaurid (Ceratosauria: Abelisauridae) from the Huincul Formation (Cenomanian-Turonian; Upper Cretaceous) of Río Negro Province, Argentina

Tralkasaurus cuyi 

 Cerroni, Motta, Agnolín, Aranciaga Rolando, Brissón Egli & Novas, 2020

DOI: 10.1016/j.jsames.2019.102445 

twitter.com/CTyS_UNLaM

Highlights: 

• We describe a new species of Abelisauride from the Huincul Formation (Cenomanian-Turonian), Rio Negro province, Patagonia, Argentina.

• Tralkasaurus cuyi nov. gen. et sp. constitutes a new form of medium-sized abelisaurid.

• The phylogenetic analysis resulted in the nesting of Tralkasaurus as a basal abelisaurid.

• The new abelisaurid affords new evidence regarding small to medium-sized abelisaurids from Patagonia.

Abstract

The record of abelisaurids in South America, particularly Argentina is relatively abundant. However, abelisaurid diversity is far from being well-known. Huincul Formation has yielded diverse theropod remains, including the abelisaurids Ilokelesia and Skorpiovenator. The aim of the present contribution is to describe a new abelisaurid coming from the Upper Section of the Huincul Formation (Cretaceous; Cenomanian-Turonian) at the Violante Farm fossil site, Río Negro province, northern Patagonia, Argentina. The new taxon described in this contribution is represented by an incomplete specimen including well-preserved maxilla and dorsal vertebrae, and distorted pelvic girdle and caudal and sacral vertebrae. Its size, much smaller than large abelisaurids as Abelisaurus and Carnotaurus indicates that the new taxon probably occupied a different ecological niche within the carnivoran guild.

Keywords: Abelisauridae, Upper Cretaceous, Río Negro province, Patagonia, Argentina

Systematic paleontology

Theropoda Marsh 1881

Ceratosauria Marsh, 1884

Abelisauroidea Bonaparte, 1991.

Abelisauridae Bonaparte and Novas, 1985.

Tralkasaurus cuyi gen. et sp. nov.

Holotype. MPCA-Pv 815 is represented by associated material including a right maxilla, distorted and incomplete dorsal, sacral and caudal vertebrae, cervical ribs, and pubis (Fig. 1).

Etymology. Tralka, means thunder in Mapudungun language, saurus means lizard in Ancient Greek; cuyi, ...

Conclusions: 

Here we described the new genus and species Tralkasaurus cuyi from Huincul Formation (Cenomanian-Turonian) beds. This new abelisaurid has a relatively small body size, as inferred from available bones. The size of Tralkasaurus contrasts with that of typical abelisaurids such as Abelisaurus and Carnotaurus, indicating that it would occupy a different ecological niche.

Furthermore, Tralkasaurus together with an unnamed abelisaurid from Cenomanian beds described by Canale et al. (2016) increases ...

 M. A. Cerroni, M. J. Motta, F. L. Agnolín, A. M. Aranciaga Rolando, F. Brissón Egli and F. E. Novas. 2020. A New Abelisaurid from the Huincul Formation (Cenomanian-Turonian; Upper Cretaceous) of Río Negro Province, Argentina. Journal of South American Earth Sciences. 98; 102445. DOI: 10.1016/j.jsames.2019.102445

 twitter.com/CTyS_UNLaM/status/1228011186656104448

[Paleontology • 2023] New Fossils of Abelisauridae (Dinosauria: Theropoda) from the upper Maastrichtian of Morocco, North Africa

in Longrich, Isasmendi, Pereda-Suberbiola & Jalil, 2023. 

DOI: 10.1016/j.cretres.2023.105677 

 twitter.com/NickLongrich 

Artwork: Andrey Atuchin

Abstract

The end of the Cretaceous saw the evolution of endemic dinosaur faunas on different landmasses, driven by continental fragmentation. Understanding the evolution of these biogeographic patterns is important for understanding the evolution of Mesozoic ecosystems. However, the faunas of the southern land masses remain understudied relative to the intensively sampled dinosaur faunas of western North America and Asia. In particular, the latest Cretaceous of Africa remains largely unknown, with only a handful of taxa reported so far, including titanosaurian sauropods, the lambeosaurine Ajnabia odysseus, and the large abelisaurid theropod Chenanisaurus barbaricus. We report two new abelisaurid fossils from the upper Maastrichtian phosphates of the Ouled Abdoun Basin, in northern Morocco. The first is the tibia of a medium-sized abelisaurid from Sidi Chennane, with an estimated length of ∼5 m. The tibia has a strongly hooked cnemial crest resembling that of the South American Quilmesaurus and Aucasaurus. The highly rugose bone texture suggest the animal was mature, rather than a juvenile of the larger Chenanisaurus. The second is a small right second metatarsal from Sidi Daoui,. The metatarsal measures 190 mm in length, suggesting a small animal, ∼2.6 m in length. The metatarsal shows strong mediolateral compression, a feature present in noasaurids and some early abelisaurids, but absent in most Late Cretaceous abelisaurids. It is distinct from other abelisauroids in the strong constriction and bowing of the shaft in lateral view, and the medial curvature of the bone in anterior view. Bone texture suggests it comes from a mature individual. The small size, gracile proportions and unusual shape of the metatarsal suggest it is not closely related to other latest Cretaceous abelisaurids. The new fossils suggest as many as three abelisaurid taxa coexisted in the upper Maastrichtian of Morocco, showing dinosaurs were highly diverse in North Africa prior to the end-Cretaceous mass extinction.

Nicholas R. Longrich, Erik Isasmendi, Xabier Pereda-Suberbiola and Nour-Eddine Jalil. 2023. New Fossils of Abelisauridae (Dinosauria: Theropoda) from the upper Maastrichtian of Morocco, North Africa. Cretaceous Research. 105677/ In Press. DOI: 10.1016/j.cretres.2023.105677

  twitter.com/NickLongrich/status/1694409571065094235

  

[Paleontology • 2022] Elemgasem nubilus • A New Brachyrostran Abelisaurid (Ceratosauria: Abelisauridae) from the Portezuelo Formation (Upper Cretaceous) of Patagonia, Argentina

Elemgasem nubilus

  Baiano, Pol, Bellardini, Windholz, Cerda, Garrido & Coria, 2022

DOI: 10.1002/spp2.1462 

  twitter.com/ThePalAss 

Abstract

Abelisaurids are medium–large-sized theropod dinosaurs that were predominant in the carnivorous fauna during the Late Cretaceous of Gondwana. These predators are abundant in the Cretaceous fossil strata of Patagonia, which yield the best record for this group. In the Late Cretaceous, abelisaurids appear in almost all regions of Gondwana and in all stages, except for the Coniacian, in which they are globally unknown. Here we describe a new abelisaurid, Elemgasem nubilus gen. et sp. nov., from the Portezuelo Formation (Turonian–Coniacian), Patagonia, Argentina. The palaeohistology of the appendicular bones of Elemgasem shows that the holotype was a subadult individual, but had achieved sexual maturity. This taxon is based on several axial and appendicular elements, and is diagnosed by the presence of a marked pattern of rugosity on the lateral surface of the fibula and a dorsoventrally deep lateral wall of the calcaneum. Moreover, the posterior caudal vertebrae have a morphology slightly different from any other abelisaurid. Elemgasem nubilus is recovered as an unstable taxon within Brachyrostra, given that it was recovered as sister taxon of Furileusauria or in several positions within this clade. Despite the problematic phylogenetic relationships of Elemgasem nubilus, it is important because it is the first abelisaurid from the Turonian–Coniacian interval and it increases the diversity of this theropod family at a time of marked turnover in the tetrapod fauna of South America, global climate change, and mass extinction events recorded worldwide in the marine realm.

Keywords: Gondwana, Turonian, Coniacian, Elemgasem, Furileusauria, abelisaurid

  Elemgasem nubilus gen. et sp. nov.

  

Mattia A. Baiano, Diego Pol, Flavio Bellardini, Guillermo J. Windholz, Ignacio A. Cerda, Alberto C. Garrido and Rodolfo A. Coria. 2022.  Elemgasem nubilus: A New Brachyrostran Abelisaurid (Theropoda, Ceratosauria) from the Portezuelo Formation (Upper Cretaceous) of Patagonia, Argentina. Papers in Palaeontology. DOI: 10.1002/spp2.1462 

  twitter.com/ThePalAss/status/1566784591133917188

[Paleontology • 2022] Guemesia ochoai • First Definitive Abelisaurid Theropod (Theropoda: Abelisauridae) from the Late Cretaceous of Northwestern Argentina

Guemesia ochoai  

Agnolín, Cerroni, Scanferla, Goswami, Paulina-Carabajal, Halliday, Cuff & Reuil, 2022

DOI: 10.1080/02724634.2021.2002348 

twitter.com/mendolaspis   twitter.com/Ch_Hendrickx

Carnotaurus sastrei Bonaparte, 1985 

 Illustration: Fred Wierum wikimedia.org

 

ABSTRACT

The fossil record of abelisaurid theropods in South America is mostly limited to Brazil and Argentina. In Argentina, abelisaurids are generally known from Patagonia, where their record is relatively abundant and includes well-known and complete specimens. However, for North-western Argentina, abelisaurids are represented by incomplete and isolated bones and teeth that remain largely unpublished. The aim of this contribution is to report a nearly complete abelisaurid braincase from the Late Cretaceous Los Blanquitos Formation (Campanian), Amblayo Valley, Salta province, Argentina. The specimen shows plesiomorphic features for abelisaurids, including a thin skull roof, absence of skull projections like horns or bulges, and low and narrow parietal eminence that lie at the same level as the sagittal crest. Furthermore, the specimen possesses some autapomorphies that support its status as a new taxon and its small size allows it to be assigned as one of the smallest abelisaurids recorded up to date. The finding of this specimen constitutes the first unequivocal occurrence of an abelisaurid in Northwestern Argentina and brings new evidence concerning the geographic distribution of the clade during Late Cretaceous times in South America.

Federico L. Agnolín, Mauricio A. Cerroni, Agustín Scanferla, Anjali Goswami, Ariana Paulina-Carabajal, Thomas Halliday, Andrew R. Cuff and Santiago Reuil. 2022.  First Definitive Abelisaurid Theropod from the Late Cretaceous of Northwestern Argentina. Journal of Vertebrate Paleontology.  e2002348. DOI: 10.1080/02724634.2021.2002348

 twitter.com/mendolaspis/status/1493740256935432195

 twitter.com/Ch_Hendrickx/status/1492158674843967493

 nhm.ac.uk/discover/news/2022/february/new-armless-abelisaur-dinosaur-species-discovered-argentina.html

 commons.wikimedia.org/wiki/File:Carnotaurus_2017.png

      

[Paleontology • 2021] The Scaly Skin of the abelisaurid Carnotaurus sastrei (Theropoda: Ceratosauria) from the Upper Cretaceous of Patagonia

Carnotaurus sastrei  Bonaparte, 1985

in Hendrickx & Bell, 2021.

DOI: 10.1016/j.cretres.2021.104994 

Illustration: J. Baardse twitter.com/LittleBaardo 

Abstract

The integument of the theropod dinosaur Carnotaurus sastrei from the Upper Cretaceous of Argentina is here described in detail for the first time. The scaly skin of this abelisaurid is the most completely preserved of any theropod and the only example of this form of integument known outside of Tetanurae (excluding footprints). The skin is preserved in the shoulder, thoracic, tail and, possibly, neck regions and consists of medium to large (20–65 mm in diameter) conical feature scales surrounded by a network of low and small (<14 mm) non-imbricating basement scales separated by narrow interstitial tissue. Contrary to previous interpretations, the feature scales are randomly distributed and neither form discrete rows nor show progressive variations in their size along parts of the body. They also show little difference in morphology along the body, although their apices are variously positioned in different body parts. Conversely, the basement scales vary from small and elongated, large and polygonal, and circular-to-lenticular in the thoracic, scapular, and tail regions, respectively. Given the presumed active lifestyle of Carnotaurus and the necessity of shedding excess heat, particularly at large body sizes (>1000 kg), we speculate that the skin may have played a vital role in thermoregulation; a role consistent with integument function in extant mammals and reptiles.

 

Keywords: Integument, Scales, Abelisauridae, Non-avian Theropoda, Skin

 Christophe Hendrickx and Phil R. Bell. 2021. The Scaly Skin of the abelisaurid Carnotaurus sastrei (Theropoda: Ceratosauria) from the Upper Cretaceous of Patagonia. Cretaceous Research. 128, 104994. DOI: 10.1016/j.cretres.2021.104994 

 twitter.com/LittleBaardo/status/1436388923614187524

twitter.com/TylerGreenfieId/status/1426322079062794240

[Paleontology • 2021] Llukalkan aliocranianus • A New Furileusaurian Abelisaurid from La Invernada (Upper Cretaceous, Santonian, Bajo De La Carpa Formation), Northern Patagonia, Argentina

Llukalkan aliocranianus 

Gianechini, Méndez, Filippi, Paulina-Carabaja, Juárez-Valieri & Garrido, 2021

DOI: 10.1080/02724634.2020.1877151 

ABSTRACT

Abelisaurids are among the most abundant and diverse Patagonian Late Cretaceous theropods. Here, we present a new furileusaurian abelisaurid, Llukalkan aliocranianus gen. et sp. nov., represented by cranial remains from the Bajo de la Carpa Formation (Santonian) at La Invernada fossil area, northwestern Patagonia. Features characterizing this taxon include a possible caudal tympanic recess posterior to the columellar recess, a T-shaped lacrimal with jugal ramus lacking a suborbital process, and large foramina for caudal middle cerebral veins widely separated from the median supraoccipital crest. In addition to this, a bulge on the anteromedial border of the supratemporal fossa, tall and posteriorly projected paroccipital processes, basal tubera interconnected distally, a triangular basisphenoid recess, and a single foramen for the sphenoidal artery on the basisphenoid, differentiate Llukalkan from Viavenator exxoni. The latter is the other furileusaurian taxon from the same area and stratigraphic unit. Although the holotype of Llukalkan probably corresponds to a sub-adult—as the lacrimal morphology suggests— the possibility that it represents a juvenile of V. exxoni is discarded based mainly on the presence of a caudal tympanic recess (which is absent in V. exxoni). The probable coexistence of two abelisaurid taxa demonstrates that the abelisaurids were one of the most important—and likely the main—predator component of the ecosystems, not only in this area, but also in all of Patagonia, during the Late Cretaceous.

FIGURE 17. Reconstruction of the complete skull and mandible of Llukalkan aliocranianus, from the Late Cretaceous of Neuquén Province, Argentina, in left lateral view.
The preserved bones are located in their supposed natural positions, whereas non-preserved parts and bones are in gray. The prearticular bone has a medial location, laterally covered by the angular and surangular. The maxilla, jugal and quadrate correspond to the right side, although they were mirrored to accommodate with the image. Scale bar equals 5 cm. For abbreviations in the figure, see text.

FIGURE 1. Provenance of the holotype of Llukalkan aliocranianus (MAU-Pv-LI-581).
 A, map showing the location of La Invernada fossil area; B, photograph of the materials in situ in the field; C, photograph showing the aspect of the outcrops of the Bajo de la Carpa Formation at La Invernada fossil area (indicated with the arrow).

SYSTEMATIC PALEONTOLOGY

THEROPODA Marsh, 1881

CERATOSAURIA Marsh, 1884

ABELISAURIDAE Bonaparte and Novas, 1985

BRACHYROSTRA Canale, Scanferla, Agnolin and Novas, 2009

FURILEUSAURIA Filippi, Méndez, Juárez Valieri and Garrido, 2016

Llukalkan aliocranianus.

Illustration: Jorge Blanco.

LLUKALKAN ALIOCRANIANUS gen. et sp. nov.

 Etymology— Llukalkan, means “one who scares or causes fear” in Mapudungun; aliocranianus means “different skull” in Latin.

Federico A. Gianechini, Ariel H. Méndez, Leonardo S. Filippi, Ariana Paulina-Carabaja, Rubén D. Juárez-Valieri and Alberto C. Garrido. 2021. A New Furileusaurian Abelisaurid from La Invernada (Upper Cretaceous, Santonian, Bajo De La Carpa Formation), Northern Patagonia, Argentina. Journal of Vertebrate Paleontology. e1877151.  DOI: 10.1080/02724634.2020.1877151 

The 'one who causes fear'—new meat-eating predator discovered

phys.org/news/2021-03-fearnew-meat-eating-predator.html

     

[Paleontology • 2021] Niebla antiqua • A New medium-sized Abelisaurid (Theropoda, Dinosauria) from the late Cretaceous (Maastrichtian) Allen Formation of Northern Patagonia, Argentina

Niebla antiqua

 Rolando, Cerroni, Marsà, Agnolín, Motta, Rozadilla, Eglí & Novas, 2021

 

DOI: 10.1016/j.jsames.2020.102915  

facebook.com/1583756585256803

Highlights: 

• A description of a new abelisaurid species from the Maastrichtian of Patagonia.

• The publication of the mid-sized abelisaurid that represents one of the smallest of the group.

• This specimen represents an adult specimen.

• Phyllogenetically represents one of the most derived of the group.

• Niebla reveals a more complex scenario for the abelisaurid evolution from the cretaceous of Patagonia.

Abstract

Abelisaurid theropods are well known in Cretaceous beds along South America, particularly Patagonia. However, the record of latest Cretaceous abelisauroids is still far from satisfactory. Until recently, few taxa were described from Maastrichtian beds: Carnotaurus sastrei and Quilmesaurus curriei, but also perhaps Abelisaurus comahuensis. In this contribution, we describe a new genus and species (Niebla antiqua gen. et sp. nov.), of medium-sized abelisaurid coming from Late Cretaceous (Maastrichtian) beds from Río Negro province, northern Patagonia, Argentina. The paleohistological analysis shows that this individual has reached the somatical maturity and that it represents an adult of a mid-sized abelisaurid. The specimen is represented by a nearly complete braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs and incomplete vertebrae. The new taxon is relatively small, much smaller than other coeval abelisaurids such as Carnotaurus and Abelisaurus. The braincase shows autapomorphic features such a dorsoventrally tall basal tuber and postemporal foramen enclosed by parietal and exoccipitals. The scapulocoracoid is notably similar to that of Carnotaurus in having a posterodorsally oriented glenoid, a dorsoventrally expanded and wide coraco-scapular plate, and a very narrow and straight scapular blade. These features are very different from those of other abelisaurids, which may indicate a unique conformation of the pectoral girdle among these South American theropods.

Keywords: Abelisauridae, Maastrichtian, South America, Paleohistology, Phylogeny, Endocranial morphology

SYSTEMATIC PALAEONTOLOGY 

Theropoda Marsh, 1881 

Ceratosauria Marsh, 1884

Abelisauroidea Bonaparte, 1991 

Abelisauridae Bonaparte and Novas, 1985 

Niebla antiqua gen. et sp. nov.

Derivation of name. Niebla, from the Spanish “mist” in reference to the foggy days during the excavation of the specimen; antiqua, comes from the Latin “old” and makes reference to the age of the specimen.

Type locality. Cerro Matadero (...), Arriagada Farm, located 70 km south from General Roca city, Río Negro province, Argentina. 

 Mauro Aranciaga Rolando, Mauricio A. Cerroni, Jordi A. Garcia Marsà, Federico l. Agnolín, Matías J. Motta, Sebastián Rozadilla, Federico Brisson Eglí and Fernando E. Novas. 2021. A New medium-sized Abelisaurid (Theropoda, Dinosauria) from the late Cretaceous (Maastrichtian) Allen Formation of Northern Patagonia, Argentina. Journal of South American Earth Sciences. 105; 102915 In Press. DOI: 10.1016/j.jsames.2020.102915 

  twitter.com/pantheo27705718/status/1316585233605513216

  twitter.com/PD_Mocho/status/1316637407756931072

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 nationalgeographicla.com/historia/2021/01/argentina-descubren-una-nueva-especie-de-dinosaurio-carnivoro-que-fue-mas-pequena 

[Paleontology • 2019] Thanos simonattoi • A New Abelisauridae (Dinosauria: Theropoda) from São José do Rio Preto Formation, Upper Cretaceous of Brazil and Comments on the Bauru Group Fauna

Thanos simonattoi 

Delcourt & Iori, 2019

 DOI: 10.1080/08912963.2018.1546700 
Art by Deverson da Silva (Pepi).

ABSTRACT

Abelisaurid theropods are well-know from the Cretaceous of several parts of the Southern Hemisphere, including South America, Madagascar, and Africa, but also in India and Europe. Abelisaurids are high-diverse among other theropods with several cervicocephalic specializations reaching medium/large sizes. In the present contribution, we describe a new abelisaurid (Thanos simonattoi, gen. et sp. nov.) from the São José do Rio Preto Formation, Bauru Group, Brazil (Upper Cretaceous). Thanos differs from other theropods by having a well-developed keel becoming wider and deeper posteriorly on the ventral surface; two lateral small foramina separated by a relative wide wall on each lateral surface of the centrum, and well-developed and deep prezygapophyseal spinodiapophyseal fossae. The closed sutures between the axis and odontoid suggest that Thanos had reached a subadult/adult stage before death. Thanos is phylogenetically related to Brachyrostra abelisaurid. The keel on the ventral axial centrum in abelisauroids is here interpreted as a homoplastic condition that became more pronounced towards the phylogeny. The presence of well-developed keel in Thanos suggests that this taxon could be more derived than other abelisaurids. Finally, even though abelisaurids could reach large sizes, Thanos shared the environment with a larger theropod that was probably close to Megaraptora.

KEYWORDS: Theropods, Brachyrostra, vertebra, axis, Thanos simonattoi

Figure 4. An interpretative picture of the paleoenvironment of São José do Rio Preto Formation (Santonian, Upper Cretaceous). The picture shows two specimens of Thanos simonattoi (on the right side) and titanosaur sauropods (on the mid and left sides).

 Art by Deverson da Silva (Pepi).

Systematic palaeontology 

Dinosauria Owen, 1842 

Theropoda Marsh, 1881 

Ceratosauria Marsh 1884 

Abelisauroidea Bonaparte and Novas, 1985 

Abelisauridae Bonaparte and Novas, 1985 

Brachyrostra Canale et al. 2009 

Thanos simonattoi gen. et sp. nov. 

Etymology: Genus name from the Greek thánato, meaning death and from the Marvel’s character Thanos, the Conquer, created by Jim Starlin. Species name in honor of Sérgio Simonatto, the discoverer of the specimen.

.....

Conclusion:

In the present contribution, we have described a new abelisaurid from the São José do Rio Preto Formation, Upper Cretaceous of Brazil. Thanos simonattoi is distinguished from other abelisaurids by having a combination of features: a well-developed keel on the ventral surface becoming wider and deeper posteriorly; two lateral small foramina separated by a relative wide wall and two welldeveloped and deep prezygapophyseal spinodiapophyseal fossae. The keel on the ventral axial centrum of Thanos is interpreted as a homoplastic condition that became more pronounced towards the phylogeny, suggesting that this taxon could be more derived than other abelisaurids. The presence of a medium-sized abelisaurid in the São José do Rio Preto Formation increases the record of theropods, suggesting a complex carnivorous fauna during the Upper Cretaceous of Bauru Group. More findings are needed to better understand the morphology and the internal relationships of Thanos simonattoi.

Rafael Delcourt and Fabiano Vidoi Iori. 2019. A New Abelisauridae (Dinosauria: Theropoda) from São José do Rio Preto Formation, Upper Cretaceous of Brazil and Comments on the Bauru Group Fauna. Historical Biology: An International Journal of Paleobiology. DOI: 10.1080/08912963.2018.1546700 

Méndez AH, Novas FE and Iori FV. 2014. New Record of Abelisauroid Theropods from the Bauru Group (Upper Cretaceous), São Paulo State, Brazil. Revista Brasileira de Paleontologia. 17(1). Citeseer: 23–32.

 Researchgate.net/publication/265381596_New_records_of_abelisauroid_theropods_from_the_Bauru_Basin_Upper_Cretaceous_Sao_Paulo_State_Brazil

 waxing-paleontological.blogspot.com/2018/11/thanos-deserves-better.html