Abstract
Relationships between the complexity of the cranial sutures and the inferred ecology of dicynodont synapsids are explored. Simple complexity indices based on degree of sutural interdigitation were calculated for 70 anomodont species and indicate that the naso-frontal sutures of Cistecephalidae, a clade inferred to be dedicated fossors based on aspects of postcranial morphology, are substantially more complex than those of other dicynodonts. The elevated complexity of the naso-frontal suture in this clade is interpreted as being related to compressive forces sustained during burrowing, paralleling the condition in some other fossorial vertebrate groups (e.g., amphisbaenians). The most highly interdigitated sutures in the cistecephalid skull are those oriented transversely to its long axis, which would experience the greatest longitudinal stresses from contact with the substrate. Although it is uncertain to what degree cistecephalid burrowing was based on scratch vs. head-lift digging, it is argued that the head played an important role during locomotion in this group. Increased sutural complexity, rather than cranial fusion, as an adaptation to resisting compressive forces during burrowing may be related to indeterminate growth in dicynodonts.
Highlights
Anomodonts were the most ecologically diverse group of herbivorous synapsids in the PermoTriassic, spanning an impressive size range and occupying a breadth of niches, including small arboreal forms, mid-sized rooters, and massive, graviportal browsers (Cruickshank, 1978; King, 1990; Surkov and Benton, 2008; Fröbisch and Reisz, 2009)
Diictodon specimens often exhibit an anterior process of the frontals, but this is a comparably minor addition to the path length of the suture
The quantitative analysis focused on the naso-frontal suture, both for its functional significance and its relative ease of measurement
Summary
Anomodonts were the most ecologically diverse group of herbivorous synapsids in the PermoTriassic, spanning an impressive size range (mature skull length from 4 to ∼100 cm) and occupying a breadth of niches, including small arboreal forms, mid-sized rooters, and massive, graviportal browsers (Cruickshank, 1978; King, 1990; Surkov and Benton, 2008; Fröbisch and Reisz, 2009). Many unusual and specialized taxa can be found amongst the expansive Permian diversity of dicynodonts, including the deep-jawed endothiodontids with their secondarily expanded tooth row, massive-skulled geikiids with their exaggerated nasal bosses, and the enigmatic, short-skulled Lanthanostegus, which may have had stereoscopic vision (Latimer et al, 1995; Modesto et al, 2002; Maisch and Gebauer, 2005).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
