Allaeochelys libyca, a New Carettochelyine Turtle from the Middle Miocene (Langhian) of Libya

Abstract

Fossil carettochelyine turtles are well known from the Paleogene of Europe (Allaeochelys), North America and Asia (Anosteira); however, the previously known Neogene fossil record is highly fragmentary and was therefore unsuitable for taxonomic analysis. In this work, we present a new carettochelyine taxon, Allaeochelys libyca, from the Middle Miocene (Langhian) of Gebel Zelten (Libya) based on an incomplete skull and disarticulated postcranial elements. The new taxon is diagnosed relative to the extant Carettochelys insculpta based on the placement of the foramen posterius canalis carotici interni close to the fenestra postotica, the horizontal orientation of the tubercula basioccipitalis, the substantial contribution of the opisthotic to the base of the tubercula basioccipitalis, the presence of a triangular pterygoid fossa, the arrangement of the mandibular condyles along a plane and the presence of an extremely well-developed fossa at the base of the processus mandibularis. A phylogenetic analysis of pancarettochelyids confirms the monophyly of Carettochelyidae and Carettochelyinae but resulted in a paraphyletic taxon, Allaeochelys. For the sake of nomenclatural stability, we provisionally retain the genus Allaeochelys as paraphyletic relative to the extant Carettochelys insculpta.

A new phylogenetic hypothesis of turtles with implications for the timing and number of evolutionary transitions to marine lifestyles in the group

“…(), Cadena (), Havlik et al . () and Zhou & Rabi () were added. We also added 58 new cranial and mandibular characters.…”

The skull of the carettochelyid turtle <i>Anosteira</i> <i>pulchra</i> from the Eocene (Uintan) of Wyoming and the carotid canal system of carettochelyid turtles

“…The majority of carettochelyid fossil finds are shell fragments (Joyce, 2014), which can be diagnostic by their highly distinct surface texture (e.g., Hutchison, 1996). Cranial remains have been reported from the Late Cretaceous of Uzbekistan (Nessov, 1977a, b, c), the Eocene of China (Danilov et al, 2017), England (Lydekker, 1889), France (Godinot et al, 2018), Germany (Harrassowitz, 1922;Joyce et al, 2012), and Spain (Joyce, 2014), and the Miocene of Libya (Havlik et al, 2014), but only a few specimens have been properly figured and described.…”

“…Gaffney (1979, fig. 173) provided a reconstruction of this fossil (FMNH PR966) under the name "Anosteira" or "Pseudanosteira", whereas Havlik et al (2014) used it to score all cranial aspects of the taxon "Anosteira pulchra", but a formal description is still missing. Given that FMNH PR966 is the only known pan-carettochelyid skull from North America, the primary purpose of this contribution is to provide a description of this fossil.…”

“…As few formal descriptions of fossil carettochelyids are available, here we compare FMNH PR966 mostly to Anosteira maomingensis (as described by Danilov et al, 2017) and Allaeochelys spp. (as described by Havlik et al, 2014, andGodinot et al, 2018).…”

“…To investigate the phylogenetic placement of Anosteira pulchra, we updated the phylogenetic analysis of Danilov et al (2017), which in return is based on Joyce (2007) and Havlik et al (2014). We accepted all changes that Danilov et al (2017) made to the matrix of Havlik et al (2014), with the exception of the following updates: (1) A. pulchra was scored 1 not ? for character 148 (see Sect.…”