An updated description of the osteology of the pancake tortoiseMalacochersus tornieri(Testudines: Testudinidae) with special focus on intraspecific variation

Abstract

Exceptional variability in the shell of the pancake tortoise Malacochersus tornieri, both in the keratinous surficial scutes and the underlying bones, in addition to its remarkably fenestrated bony shell are unique among tortoises. Based on 14 individuals of different sizes and ages, the observed variation in M. tornieri was described in detail, with additional notes on the typically testudinid skull, inner ear and brain endocast using microCT-scan data, as well as the limbs. Similar degrees of variation have not yet been described in any other extant turtle species and therefore seem notable in M. tornieri, and might be related to the species' unique lifestyle. Within the carapace, the peripherals and suprapygals are most variable in number. Furthermore, different combinations of peripherals are participating in the central plastral fontanelle and in some individuals additional bones take part in the formation of the plastron. J. Morphol. 278:321-333, 2017. © 2017 Wiley Periodicals, Inc.

Sensory Evolution and Ecology of Early Turtles Revealed by Digital Endocranial Reconstructions

“…The anterior and posterior semicircular canals (ASC and PSC, respectively) are nearly at the same level as the lateral semicircular canal (LSC), whereas in other turtles the first two run dorsally in relation to the last Mautner et al, 2017;PaulinaCarabajal et al, 2017;Ferreira et al, 2018). The angle between the ASC and LSC is also very wide (Table 1), with similar values to meiolaniids and tortoises (Paulina-Carabajal et al, 2017).…”

“…Its endocast is a relatively simple structure when compared to that of crownturtles Mautner et al, 2017;PaulinaCarabajal et al, 2017;Ferreira et al, 2018). It has a tube-like shape, with only small pontine and cephalic flexures and poorly differentiated brain regions.…”

“…The anterior and posterior semicircular canals are small and anteroposteriorly longer than high and have low internal radii. The crus communis is also very low in comparison to other taxa Mautner et al, 2017;Paulina-Carabajal et al, 2017;Ferreira et al, 2018) which results in an almost horizontal orientation of the anterior and posterior semicircular canals (Figure 4). The lateral semicircular canal barely extends laterally from the vestibulum.…”

“…Some regions became more pronounced as well. In N. speciosa, meiolaniids (Paulina-Carabajal et al, 2017), Plesiochelys etalloni and all other crown-turtles (Mautner et al, 2017;Ferreira et al, 2018) the cerebral hemispheres are clearly distinguishable from the remainder of the endocast and are wider in relation to skull and endocast length than in P. quenstedti (Figures 2, 3). The olfactory bulb can also be seen in the endocasts of some taxa, e.g., Testudo graeca and Plesiochelys etalloni Paulina-Carabajal et al, 2017).…”

New turtle remains from the Late Cretaceous of Monte Alto-SP, Brazil, including cranial osteology, neuroanatomy and phylogenetic position of a new taxon

“…The fenestra ovalis is smaller than that of Malacochersus tornieri (Mautner et al 2017). The columella 444 auris is preserved on both sides (Fig.…”