Open Paleo

Eoabelisaurus

Pol & Rauhut, 2012 EE-o-ah-BEL-i-SOR-us /ˈioʊəˌbɛlɪˈsɔːrəs/

From Greek 'eos' (ἠώς) meaning 'dawn' combined with the genus name Abelisaurus, indicating it is an early (dawn) relative of Abelisaurus.

174.7–168.2 million years ago Aalenian–Bajocian, Middle Jurassic
Middle Jurassic stages

Eoabelisaurus is a genus of ceratosaurian theropod dinosaur from the Middle Jurassic Cañadón Asfalto Formation of the Cañadón Asfalto Basin in Argentina, South America. The generic name combines a Greek ἠώς, (eos), "dawn", with the name Abelisaurus, in reference to the fact it represents an early relative of the latter. Only one species is currently recognized, E. mefi; the specific name honors the MEF, the Museo Paleontológico "Egidio Feruglio", where discoverer Diego Pol is active. Its forelimb combines an unreduced humerus with a shortened forearm and a short, robust hand, which its describers read as an early stage of the forelimb reduction seen in abelisaurids.

Under dispute

Pol and Rauhut (2012) and Zaher and colleagues (2020) recovered Eoabelisaurus as the basalmost abelisaurid, and Pol and colleagues (2024) placed it among the basal branches of Abelisauridae by parsimony but outside Abelisauroidea in their Bayesian analysis. Tortosa and colleagues (2014), Filippi and colleagues (2016) and Delcourt (2017) recovered it as the basalmost abelisauroid, while Farke and Sertich (2013), Cerroni and colleagues (2020) and Aranciaga Rolando and colleagues (2020) placed it just outside Abelisauroidea. Wang and colleagues (2016) recovered it as the basalmost ceratosaurid, and Hendrickx and colleagues (2024) as a neoceratosaur outside both Ceratosauridae and Abelisauroidea. Placed at Ceratosauria incertae sedis, the least inclusive clade common to these readings.

Diagnosis

  1. Quadrate with thickened medial distal articular end and subparallel articular condyles.
  2. Mid-dorsal vertebrae with double, V-shaped lamina extending from the parapophysis to the prezygodiapophyseal lamina.
  3. Ulna with hypertrophied olecranon process accounting for more than 30 per cent of its length.
  4. Pubic foramen elongate, more than twice as long as high.
  5. Ambiens process of pubis developed as a large, anterolaterally directed, convex expansion.

Species

Eoabelisaurus mefi Pol & Rauhut, 2012

Type species

Named for the MEF — the Museo Paleontológico 'Egidio Feruglio' in Argentina — the institution where discoverer Diego Pol is active.

Holotype
MPEF PV 3990 , Museo Paleontológico "Egidio Feruglio"
Material
Nearly complete skeleton with skull, subadult or adult individual
Horizon
Cañadón Asfalto Formation, Aalenian–Bajocian, Middle Jurassic , 174.7–168.2 million years ago
Locality
Jugo Loco, Chubut, Argentina

References

  1. Pol, D.; Rauhut, O. W. M. (2012). A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs. Proceedings of the Royal Society B: Biological Sciences 279(1741): 3170-3175. The Royal Society. doi:10.1098/rspb.2012.0660

    Gives the Jugo Loco locality as finely bedded mud-, marl- and limestones of the Cañadón Asfalto Formation, early Middle Jurassic (Aalenian-Bajocian), the source of the age.

    pol2012a
  2. Cúneo, R.; Ramezani, J.; Scasso, R.; Pol, D.; Escapa, I.; Zavattieri, A. M.; Bowring, S. A. (2013). High-precision U-Pb geochronology and a new chronostratigraphy for the Cañadón Asfalto Basin, Chubut, central Patagonia: implications for terrestrial faunal and floral evolution in Jurassic. Gondwana Research 24(3-4): 1267-1275. Elsevier BV. doi:10.1016/j.gr.2013.01.010

    Dates the interval overlying the uppermost basalt flow at Cerro Cóndor, which holds this taxon, as Aalenian to probably Bajocian, with a latest Toarcian age not precluded near the basalt.

    cúneo2013a
  3. Zaher, H.; Pol, D.; Navarro, B. A.; Delcourt, R.; Carvalho, A. B. (2020). An Early Cretaceous theropod dinosaur from Brazil sheds light on the cranial evolution of the Abelisauridae. Comptes Rendus Palevol (6). Museum National D'Histoire Naturelle. doi:10.5852/cr-palevol2020v19a6

    Recovered Eoabelisaurus as the most basal member within Abelisauridae.

    zaher2020a
  4. Pol, D.; Baiano, M. A.; Černý, D.; Novas, F. E.; Cerda, I. A.; Pittman, M. (2024). A new abelisaurid dinosaur from the end Cretaceous of Patagonia and evolutionary rates among the Ceratosauria. Cladistics 40(3): 307-356. Wiley. doi:10.1111/cla.12583

    Recovered Eoabelisaurus among the basal branches of Abelisauridae by parsimony, but outside Abelisauroidea, as sister to Xenotarsosaurus, in a Bayesian analysis; both results are weakly supported.

    pol2024a
  5. Farke, A. A.; Sertich, J. J. W. (2013). An Abelisauroid Theropod Dinosaur from the Turonian of Madagascar. PLoS ONE 8(4): e62047. Public Library of Science (PLoS). doi:10.1371/journal.pone.0062047

    Recovered Eoabelisaurus as a non-abelisauroid ceratosaur, sister to Abelisauroidea, with two extra steps needed to force it into Abelisauridae.

    farke2013a
  6. Tortosa, T.; Buffetaut, E.; Vialle, N.; Dutour, Y.; Turini, E.; Cheylan, G. (2014). A new abelisaurid dinosaur from the Late Cretaceous of southern France: Palaeobiogeographical implications. Annales de Paléontologie 100(1): 63-86. Elsevier BV. doi:10.1016/j.annpal.2013.10.003

    Recovered Eoabelisaurus with Berberosaurus as the basalmost members of Abelisauroidea, outside Abelisauridae.

    tortosa2014a
  7. Filippi, L. S.; Méndez, A. H.; Juárez Valieri, R. D.; Garrido, A. C. (2016). A new brachyrostran with hypertrophied axial structures reveals an unexpected radiation of latest Cretaceous abelisaurids. Cretaceous Research 61: 209-219. Elsevier BV. doi:10.1016/j.cretres.2015.12.018

    Recovered Eoabelisaurus as the basalmost abelisauroid, extending the Tortosa and colleagues (2014) dataset.

    filippi2016a
  8. Delcourt, R. (2017). Revised morphology of Pycnonemosaurus nevesi Kellner & Campos, 2002 (Theropoda: Abelisauridae) and its phylogenetic relationships. Zootaxa 4276(1): 1-45. doi:10.11646/zootaxa.4276.1.1

    Recovered Eoabelisaurus as the basalmost abelisauroid on a modified Filippi and colleagues (2016) dataset.

    delcourt2017a
  9. Cerroni, M. A.; Motta, M. J.; Agnolín, F. L.; Aranciaga Rolando, A. M.; Brissón Egli, F.; Novas, F. E. (2020). A new abelisaurid from the Huincul Formation (Cenomanian-Turonian; Upper Cretaceous) of Río Negro province, Argentina. Journal of South American Earth Sciences 98. Elsevier BV. doi:10.1016/j.jsames.2019.102445

    Recovered Eoabelisaurus as the sister taxon of Abelisauroidea on the Filippi and colleagues (2016) dataset.

    cerroni2020a
  10. Aranciaga Rolando, M.; Cerroni, M. A.; García Marsà, J. A.; Agnolín, F. L.; Motta, M. J.; Rozadilla, S.; Brissón Egli, F.; Novas, F. E. (2020). 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. Elsevier BV. doi:10.1016/j.jsames.2020.102915

    Recovered Eoabelisaurus as the sister taxon of Ligabueino plus Abelisauroidea on the Filippi and colleagues (2016) dataset.

    aranciagarolando2020a
  11. Wang, S.; Stiegler, J.; Amiot, R.; Wang, X.; Du, G. H.; Clark, J. M.; Xu, X. (2016). Extreme Ontogenetic Changes in a Ceratosaurian Theropod. Current Biology 27(1): 144-148. doi:10.1016/j.cub.2016.10.043

    Recovered Eoabelisaurus as the basalmost member of Ceratosauridae, a clade this analysis nests within Abelisauridae.

    wang2016b
  12. Hendrickx, C.; Cerroni, M. A.; Agnolín, F. L.; Catalano, S.; Ribeiro, C. F.; Delcourt, R. (2024). Osteology, relationship, and feeding ecology of the theropod dinosaur Noasaurus leali, from the Late Cretaceous of North-Western Argentina. Zoological Journal of the Linnean Society 202(4): zlae150. doi:10.1093/zoolinnean/zlae150

    Recovered Eoabelisaurus on two revised datasets, as a neoceratosaur between Ceratosauridae and Abelisauroidea in one and as the sister taxon of Ceratosauridae plus Abelisauridae in the other.

    hendrickx2024a