Sunday, April 23, 2017

[Paleontology • 2017] Isaberrysaura mollensis • A New Primitive Neornithischian Dinosaur from the Jurassic of Patagonia with Gut Contents

 Isaberrysaura mollensis
Salgado, Canudo, Garrido, Moreno-Azanza, Martínez, Coria & Gasca, 2017

DOI: 10.1038/srep42778 

We describe a new species of an ornithischian dinosaur, Isaberrysaura mollensis gen. et sp. nov. The specimen, consisting in an almost complete skull and incomplete postcranium was collected from the marine-deltaic deposits of the Los Molles Formation (Toarcian-Bajocian), being the first reported dinosaur for this unit, one of the oldest from Neuquén Basin, and the first neornithischian dinosaur known from the Jurassic of South America. Despite showing a general stegosaurian appearance, the extensive phylogenetic analysis carried out depicts Isaberrysaura mollensis gen. et sp. nov. as a basal ornithopod, suggesting that both Thyreophora and neornithischians could have achieved significant convergent features. The specimen was preserved articulated and with some of its gut content place in the middle-posterior part of the thoracic cavity. Such stomach content was identified as seeds, most of them belonging to the Cycadales group. This finding reveals a possible and unexpected role of this ornithischian species as seed-dispersal agent.

Figure 2: Isaberrysaura mollensis gen. et sp. nov. holotype.
 Skull in dorsal (a and b, photograph and drawing respectively), and left lateral (c and d, photograph and drawing respectively) views. (e) Premaxillary tooth; (f,g) maxillary teeth (g inverted).
amf, anterior maxillary fossa; aof, antorbital fossa; aso, anterior supraorbital; d, dentary; ef, elliptical fossa; f, foramina; fr, frontal; ift, infratemporal fenestra; j, jugal; mx, maxilla; n, nasals; o, orbit; pd, predentary; pdb, postdentary bones; pmx, premaxilla; po, postorbital; pso: posterior supraorbital; prf, prefrontal; qj, quadratojugal; sq, squamosal; stf, supratemporal fenestra. 1–7 denticles. 

Figure 3 Gut content of Isaberrysaura mollensis gen. et sp. nov.
(a–c), seeds of cycads (c), and other seeds (s); rib (r). (d,e) Detail of seeds of cycads: sarcotesta (sa), sclerotesta (sc), coronula (c), nucellus (n). (f) Location of the gut content in the reconstructed skeleton of Isaberrysaura mollensis gen. et sp. nov.  

Systematic palaeontology

Ornithischia Seeley, 1887
Genasauria Sereno, 1986

Neornithischia Sereno, 1986

Isaberrysaura mollensis gen. et sp. nov.

Etymology: In honour of Isabel Valdivia Berry, who reported the finding of the holotype material.

Holotype: MOZ-Pv 6459. A skeleton comprising a nearly complete skull, and a partial postcranium (still unprepared) consisting of 6 cervical vertebrae, 15 dorsal vertebrae, a sacrum with a partial ilium and an apparently complete pubis, 9 caudal vertebrae, part of a scapula, ribs, and unidentifiable fragments.

Type locality and horizon: The holotype comes from the locality of Los Molles (Neuquén Province, Argentina) (Fig. 1). The specimen was found in the marine-deltaic deposits of the Los Molles Formation (Toarcian-Bajocian), which in this sector reaches a thickness of approximately 1,042 m. The fossil-bearing level is composed of laminated pelites rich in ammonitiferous concretions and vertebrate remains, located some 40 m below the contact with the overlying unit (Lajas Formation, Bajocian-Bathonian). The presence of the ammonite Sonninia altecostata allows the fossil-bearing level to be situated biochronologically in the early Bajocian. In palaeoenvironmental terms, the sedimentary succession comprises a large-scale progradational deltaic system, dominated by wave action and the influence of storms. The dinosaur remains described here, the first reported from this unit, are among the oldest from Neuquén Basin.

Leonardo Salgado, José I. Canudo, Alberto C. Garrido, Miguel Moreno-Azanza, Leandro C. A. Martínez, Rodolfo A. Coria and José M. Gasca. 2017. A New Primitive Neornithischian Dinosaur from the Jurassic of Patagonia with Gut Contents. Scientific Reports. 7: 42778. DOI: 10.1038/srep42778

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