Friday, April 22, 2016

[Paleontology • 2016] First Sauropod Bones from Italy Offer New Insights on The Radiation of Titanosauria between Africa and Europe


Titanosauria gen. et sp. indet.
Possible reconstruction of the Italian sauropod 

Highligths
• Referable to Titanosauria gen. et sp. indet., earliest record in southern Europe.
• An Aptian–Albian basal titanosaurian with bizarre orientation of the zygapophyseal facets.
• Further evidence of Early Cretaceous sporadic connection between Africa and Europe.

Abstract
Here we describe the first sauropod skeletal remains from the Italian peninsula that also represent the earliest record of titanosaurs in Southern Europe. Scattered bones, including an almost complete anterior caudal vertebra, were found in Cretaceous (Aptian–Albian) marine deposits, some 50 km East of Rome. The vertebra shows a bizarre and perhaps unique orientation of the zygapophyseal articular facets that renders their interpretation problematic. Phylogenetic retrofitting tests support the placement of the Italian titanosaur among basal lithostrotians. Palaeobiogeographic analysis based on the resulting phyletic relationships suggests an Afro-Eurasian route for the ancestors of the Italian titanosaur, a scenario compatible with the palaeogeographic evolution of the Italian microplates during the Cretaceous. Together with previously recorded titanosaurian-like ichnites from a Cenomanian locality in Latium, this new find suggests a quite long emersion for the Apenninic carbonate platform. We suggest that the Italian titanosaur was member of a population that crossed the western Tethys Sea through a “filtering bridge” composed of a chain of ephemeral islands and peninsulae, known as Periadriatic (Adria) carbonate platforms, that connected sporadically Africa and Europe since the Early Cretaceous.

Keywords: Sauropoda; Titanosauria; Early Cretaceous; Aptian–Albian; Italy; Palaeobiogeography




Systematic palaeontology

Dinosauria Owen, 1842
Saurischia Seeley, 1887
Sauropoda Marsh, 1878

Titanosauriformes Salgado, Coria and Calvo, 1997
Titanosauria Bonaparte and Coria, 1993

Titanosauria gen. et sp. indet.

Material: Three disarticulated bones, deposited at the Museo di Storia Naturale di Milano (MSNM), Milan, Italy: one anterior caudal vertebra (MSNM V7157), one portion of scapular blade or of ischial/pubic shaft (MSNM V7158), and another -possibly pelvic- bone fragment (MSNM V7159).

Fig. 1. Map of Italy showing Latium (red) and the Monti Prenestini position (blue), and geological map of the Rocca di Cave area with stratigraphic log of the outcrop that contained the new titanosaurian bones. The blue target indicates the discovery site (modified from Praturlon and Madonna, 2007).
(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)  DOI:  10.1016/j.cretres.2016.03.008

  Horizon, age and locality: Monti Prenestini carbonate platform, “Ostracod and Gastropod limestones” unit (sensu Praturlon and Madonna, 2007); Lower Cretaceous, upper Aptian–lower Albian; Rocca di Cave, Palestrina, Roma Province, Italy (locality coordinates on file at the Soprintendenza Archeologia del Lazio e dell'Etruria meridionale).

  Remarks
The following combination of phylogenetically informative features permits to refer MSNM V7157 to a titanosaurian sauropod, and more precisely to a basal lithostrotian: anterior caudal vertebra strongly procoelous, with the apex of the articular condyle positioned on the dorsal half of the centrum; centrum height and width subequal; chevron attachments for single articular facets; pedicles of the neural arch short and attached to the anterior half of the centrum; neural spine vertically projecting; long prezygapophyses (about 40% of the centrum length), evidently surpassing the cranial end of the centrum; prezygapophyseal articular facets widened by a bony rim; postzygapophyses nested at the base of the neural spine and terminating at the level of the centrum-condyle rim; tubercle on spinoprezygapophyseal lamina near prezygapophysis; postzygapophyseal centrodiapophyseal fossa and postzygapophyseal spinodiapophyseal fossa almost confluent; inner bone structure apneumatic.

A bizarre feature observed in MSNM V7157 is that the prezygapophyseal facets face medioventrally rather than mediodorsally, and that the postzygapophyseal facets face laterodorsally rather than lateroventrally, diverging ventrally and widening the intrapostzygapophyseal lamina into a large pyramidal bony bridge. The absence of a ventral longitudinal hollow in the centrum is here interpreted a reversion to the plesiomorphic condition exhibited by basal, non-lithostrotian titanosaurs (see Section 6).

.......

 Cristiano Dal Sasso, Gustavo Pierangelini, Federico Famiani, Andrea Cau and Umberto Nicosia. 2016. First Sauropod Bones from Italy Offer New Insights on The Radiation of Titanosauria between Africa and Europe. Cretaceous Research.  DOI:  10.1016/j.cretres.2016.03.008


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