Embryonic Skulls of Titanosaur Sauropod Dinosaurs

Abstract

Little is known about the cranial anatomy of the taxonomically diverse and geographically widespread titanosaurs, a paucity that has hindered inferences about the genealogical history and evolutionary development of the latest sauropod dinosaurs. Newly discovered fossil eggs containing embryonic remains from the Late Cretaceous of Argentina provide the first articulated skulls of titanosaur dinosaurs. The nearly complete fetal skulls shed light on the evolution of some of the most notable cranial features of sauropod dinosaurs, including the retraction of the external nares, the forward rotation of the braincase, and the abbreviation of the infraorbital region.

Taphonomical and palaeoecological investigation of the Late Cretaceous (Maastrichtian) Tuştea vertebrate assemblage (Romania; Haţeg Basin) - insights into a unique dinosaur nesting locality

“…Megaloolithid eggs are customarily considered to have been laid by titanosaurian sauropods (e.g., Mikhailov, 1997;Horner, 2000;Chiappe et al, 2005;García et al, 2015), a hypothesis that is supported by perinatal titanosaurian remains discovered associated with different megaloolithid ootaxa in Argentina (Chiappe et al, 1998(Chiappe et al, , 2001(Chiappe et al, , 2003(Chiappe et al, , 2005 and India (Wilson et al, 2010). Accordingly, the Tuștea eggs were also referred to titanosaurian sauropods by Grigorescu et al (1990), as well.…”

“…(1) There is a wide consensus that the Megaloolithus oogenus belongs exclusively to titanosaurian sauropods (e.g., Buffetaut and Le Loeuff, 1994;Sahni and Khosla, 1994;Mohabey, 1996;Chiappe et al, 1998Chiappe et al, , 2001Chiappe et al, , 2003Chiappe et al, , 2005Horner, 2000;Salgado et al, 2007;Jackson et al, 2008;Wilson et al, 2010;Sellés et al, 2013;García et al, 2015). Furthermore, reports of megaloolithid eggs that include in ovo titanosaur embryos from the Early Cretaceous locality of Algui Ulaan Tsav in Mongolia (Grellet-Tinner et al, 2011) and the Late Cretaceous localities of Auca Mahuevo in Patagonia, Argentina (Chiappe et al, 1998(Chiappe et al, , 2005, as well as that of the co-occurrence of one titanosaur hatchling and megaloolithid eggs at Dholi Dungri in India (Wilson et al, 2010), allow confident association of certain megaloolithid eggshell types with titanosaurs.…”

Oology and the evolution of thermophysiology in saurischian dinosaurs: homeotherm and endotherm deinonychosaurians?

“…In the fossil record, the former requires the rare preservation of a female with eggs in its reproductive system (Sato et al, 2005), the latter is relatively more often recorded (Currie and Horner, 1988;Horner and Weishampel, 1988;Horner and Currie, 1994;Norell et al, 1994Norell et al, , 2001Horner, 1997;Manning et al, 1997;Mateus et al, 1997;Chiappe et al, 2001a;Schweitzer et al, 2002). These discoveries have also allowed the association of eggs of several extinct dinosaurs to species-specific nest structures (Varricchio et al, 1997;Chiappe et al, 2004) and in some instances, to species-specific nesting behaviors (Norell et al, 1995;Dong and Currie, 1996;Clark et al, 1999;Varricchio et al, 1999;Grellet-Tinner et al, 2006).…”

“…Nevertheless, taphonomic and taxonomic levels of confidence (two different indices) might differ for a given oological specimen according to its proximity to specific skeletal remains and it's posteriori taxonomic identification, thus could foster erroneous phylogenetic and paleobiological interpretations. As such, the highest level of taphonomic confidence in the association of fossil eggs with skeletal remains occurs when diagnostic embryos are found in ovo (Norell et al, 1994(Norell et al, , 2001Chiappe et al, 2001a) or when eggs are preserved inside a gravid female (Sato et al, 2005). However, a high taphonomic level does not always correspond to a first level of taxonomic confidence.…”

Stratigraphic and taphonomic analysis of Bonitasaura salgadoi Apesteguía (Sauropoda, Titanosauria) at «La Bonita» site (Upper Cretaceous, Río Negro Province, Argentina)

“…Los elementos 00 (cuadrado), 01 (dentario), 02 (frontal), 03 (parietal) y 67 (tibia) no se encuentran mapeados. briones de la localidad Auca Mauhida (=Auca Mahuevo) (Chiappe et al, 1998;Chiappe et al, 2001;Dingus et al, 2000). En el sitio «La Bonita», la Fm.…”