Sensory Evolution and Ecology of Early Turtles Revealed by Digital Endocranial Reconstructions
Stephan Lautenschlager, Gabriel S. Ferreira, Ingmar Werneburg · 2018 · 74 citationsRead the paper
In the past few years, new fossil finds and novel methodological approaches have prompted intensive discussions about the phylogenetic affinities of turtles and rekindled the debate on their ecological origin, with very distinct scenarios, such as fossoriality and aquatic habitat occupation, proposed for the earliest stem-turtles. While research has focused largely on the origin of the anapsid skull and unique postcranial anatomy, little is known about the endocranial anatomy of turtles. Here, we provide 3D digital reconstructions and comparative descriptions of the brain, nasal cavity, neurovascular structures and endosseous labyrinth of Proganochelys quenstedti, one of the earliest stem-turtles, as well as other turtle taxa. Our results demonstrate that P. quenstedti had retained a simple tube-like brain morphology with poorly differentiated regions and mediocre hearing and vision, but a well-developed olfactory sense. Endocast shape analysis indicates that an increase in size and regionalization of the brain took place in the course of turtle evolution, achieving an endocast diversity comparable to other amniote groups. Based on the new evidence, we further conclude that P. quenstedti was a highly terrestrial, but most likely not a fossorial taxon
What the full text shows
Shown in the lab- Proganochelys quenstedti possessed a simple tube-like brain morphology with poorly differentiated regions and the lowest endocast volume to basicranial length ratio in the sample. (Compared to crown-turtles and other sampled taxa)
- P. quenstedti had a well-developed olfactory sense, with the olfactory nerve contributing a significant portion of the endocast length. — 1/3 to 1/2 of the full endocast length (Based on digital reconstructions of MB 1910.45.2 and SMNS 16980)
- P. quenstedti exhibited mediocre hearing and vision. (Based on endosseous labyrinth and optic nerve canal reconstructions)
- The brain of turtles increased in size and regionalization over evolutionary time, reaching diversity comparable to other amniotes. (Based on endocast shape analysis across stem and crown turtles)
- P. quenstedti was a highly terrestrial taxon and likely not fossorial. (Based on endocranial and sensory evidence)
- P. quenstedti possesses a pendant pituitary fossa, a feature common in archosaurs but absent in extant turtles. (Compared to extant turtle taxa)
- Setup
- Two specimens of P. quenstedti (MB 1910.45.2 and SMNS 16980), one stem-turtle (Naomichelys speciosa), and nine extant turtle species.
- How
- The researchers used CT scanning (medical and micro-CT) and digital segmentation in Avizo to create 3D reconstructions of the endocranium. They performed a 2D outline shape analysis using tpsDig2.16 on sagittal cross-sections to quantify morphological differences across taxa.
- Limitations
- Specimen MB 1910.45.2 exhibited moderate medio-lateral deformation and anteroposterior shearing. · Poor grayscale contrast in SMNS 16980 limited the visualization of some structures. · Shape analysis relied on 2D outlines rather than 3D landmarks due to a lack of homologous landmarks across taxa.
Summarized by Gemma 4 from the open-access full text · 7 Oct 2026. Read it