Revision of Sulcusuchus erraini (Sauropterygia, Polycotylidae) from the Upper Cretaceous of Patagonia, Argentina

Abstract

O’Gorman, J.P. & Gasparini, Z., 2013. Revision of Sulcusuchus erraini (Sauropterygia, Polycotylidae) from the Upper Cretaceous of Patagonia, Argentina. Alcheringa 37, 161–174. ISSN 0311-5518.

Sulcusuchus erraini, from the upper Campanian–lower Maastrichtian of Patagonia, Argentina, is the only polycotylid from the Southern Hemisphere for which the skull and mandible are known. The diagnosis of the species and genus is emended based on new observations. Sulcusuchus is characterized by the following autapomorphies: (1) deep and broad rostral and mandibular grooves and (2) a wide notch on the posterior margin of the pterygoids that are combined with a part of the body of the basioccipital, forming a wide plate. Several hypotheses about the identity of the structures that could have been housed in the rostral and mandibular grooves are evaluated. Only two of several hypotheses were not discarded. The first is that the grooves may have accommodated oral glands (supralabial and sublabial), but the biological role of such glands could not be inferred. The second hypothesis is the presence of special structures of an electrosensitive and/or mechanosensitive nature, which might allow the detection of infaunal or semi-infaunal food in soft substrates, as is represented in modern analogues, such as dolphins.

José P. O’Gorman [[email protected]] and Zulma Gasparini [[email protected]], División Paleontología Vertebrados, Museo de La Plata, Universidad Nacional de La Plata, Paseo del Bosque s/n., B1900FWA La Plata, Argentina. Also affiliated with Consejo Nacional de Investigaciones Científicas y Técnicas, Av. Rivadavia 1917 (C1033AAJ), Ciudad Autónoma de Buenos Aires, Argentina and CONICET: Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina Received 5.6.2012; revised 31.7.2012; accepted 4.9.2012.

阿根廷Patagonia的Campanian阶上部至Maastrichtian阶下部的Sulcusuchus erraini是南半球唯一的polycotylid。关于这个种, 已知的仅是头骨和下颚。种和属的鉴定标准根据新发现得以修改。Sulcusuchus有下列特征: (1)深且宽的吻端和下颌沟槽和(2)翼状软骨的后缘上的宽刻缺;翼状软骨与部分颅底骨一起形成–个宽板。我们对关于吻端和下颌沟槽内究竟装载什么构造的若干假设进行了检验, 最后只剩两个假设没被抛弃。第一个假设是, 沟槽可以装载口腺体, 但这种口腺体的生物作用还未推测出来。第二个假设是, 这个特殊构造具有电感应和/或机械感应性质, 可能用来探测软基底中的食物–内生动物和半内生动物, 就像海豚一样。

Key words:

• Plesiosauria
• La Colonia Formation
• Los Alamitos Formation
• Campanian
• Maastrichtian

Acknowledgements

The authors thank D. Pol and E. Ruigómez (Museo Paleontológico E. Feruglio, Trelew, Argentina) for the loan of MPEF 650 for this revision, and D. Verzi (Museo de La Plata, Argentina) for access to the collections of pontoporid cetaceans. Likewise, we thank C. Deschamps and M. Tomeo (Museo de La Plata) for the editing the manuscript and M. Sosa for the drawings. The authors also give thanks to L. Salgado (Universidad Nacional del Comahue), C. Deschamps, P. Bonna (Museo de La Plata), A. Parras (Universidad Nacional de La Pampa), and A. Paulina Carabajal (Museo Carmen Funes, Plaza Huincul) for reading early versions of this manuscript. The authors especially thank M. Fernández (Museo de La Plata) for constructive suggestions that improved the manuscript. The authors are also thankful for the comments of two anonymous reviewers and the editor, Stephen McLoughlin, that have improved this manuscript. This research was funded by PICT 2008-0261 (Agencia de Promoción Científica y Tecnológica, Argentina) and UNLP N607 (Universidad Nacional de La Plata, Argentina).