The case of the grass-eating suids in the Plio-Pleistocene Turkana Basin: 3D dental topography in relation to diet in extant and fossil pigs

Technical note: A freeware, equitable approach to dental topographic analysis

Dental topographic analysis has proved a valuable tool for quantifying dental morphology. Established workflows often use proprietary software for pre-processing dental surfaces, rendering the method expensive and inaccessible to many. This study explores the use of freeware pre-processing alternatives. We tested 4 decimation tools and 13 smoothing tools across 7 different freeware packages. Surfaces generated via proprietary software could not be replicated, but it was possible to obtain statistically similar measurements using freeware. Based on this investigation, we propose a freeware workflow for researchers to conduct dental topographic analysis, with the expectation that their results will be comparable to that obtained through proprietary methods.

Dental topographic and three-dimensional geometric morphometric analysis of carnassialization in different clades of carnivorous mammals (Dasyuromorphia, Carnivora, Hyaenodonta)

The evolution of carnassial teeth in mammals, especially in the Carnivora, has been subject of many morphometric and some dental topographic studies. Here, we use a combination of dental topographic analysis (Dirichlet normal energy) and 3D geometric morphometrics of less and high carnassialized lower teeth of carnivoran, dasyuromorph and hyaenodont taxa. Carnassial crown curvature, as indicated by Dirichlet normal energy, is high in lesser carnassialized teeth and low in higher carnassialized teeth, where it is influenced by the reduction of crown features such as cusps and crests. PC1 of the geometric morphometric analysis is linked to enlargement of the carnassial blade, reduction of the talonid crushing basin and an increasingly asymmetric cervix line with an enlarged mesial flexure in more carnassialized teeth. Distribution of PC1 values further indicates that along the tooth row of dasyuromorphs (m2-m4) and hyaenodonts (m1-m3) the most distal carnassial is the most carnassialized (principal carnassial), and in most taxa with overall higher carnassialized teeth, carnassialization successively increases from the anterior to the posterior tooth position along the tooth row. PC2 indicates that a longitudinal elongated carnassial is present in caniforms and in unspecialized feliforms, which separates these taxa in morphospace from all dasyuromorphs, hyaenodonts and specialized feliforms. An ancestral state reconstruction shows that this longitudinal elongation may be a plesiomorphic ancestral state for the Carnivora, which is different from the Dasyuromorphia and the Hyaenodonta. This elongation, enabling the presence of a longitudinally aligned carnassial blade as well as a complete talonid basin, might have provided the Carnivora with an advantage in terms of adaptive versatility.

Quantitative analyses of squamate dentition demonstrate novel morphological patterns

Squamates are ideal subjects for investigating relationships between diet and dental patterns because they exhibit wide dietary diversity, marked variation in dental shape, and are taxonomically abundant. Despite this, well-established links between diet and dental morphology are primarily qualitative in nature, with specific patterns of squamate dental complexity remaining largely unknown. Here, we use quantitative methods and a broad taxonomic dataset to quantify key patterns in squamate dental morphology, including re-examining the relationship between dentition and diet, testing for differences in complexity between dentigerous elements, and exploring the effect of ontogenetic dietary shifts in dental complexity in two iguanid genera. Our findings support previous research by demonstrating that species consuming more plant material possess more complex teeth. We did not find significant complexity differences between the left and right dentigerous elements nor the upper and lower jaws, with the exception of Amblyrhynchus cristatus, the marine iguana, which possesses significantly more complex dentary teeth than premaxillary and maxillary teeth. We find discordant patterns when testing for dental complexity changes through ontogeny. Amblyrhynchus, which is primarily herbivorous throughout its lifetime, increases dental complexity through ontogeny, whereas Ctenosaura, which is generally insectivorous as juveniles and herbivorous as adults, decreases dental complexity. Although preliminary, this research documents and quantifies novel patterns of squamate dental complexity and exhibits the possibilities for further research on the diversity of squamate dental morphology.

Anomalous erosion patterns on the cheek teeth of babirusa (genus Babyrousa)

Two types of anomalous erosive wear, designated “Wear” and “Groove”, were found in the molar teeth of adult babirusa (genus Babyrousa Perry, 1811) species from Buru or the Sula Islands and Sulawesi, Indonesia. A survey of 590 specimens of babirusa crania and mandibles from international museums and private collections revealed their presence in 20 of 187 specimens from Buru or the Sula Islands, in 99 of 391 specimens from Sulawesi, and in 4 of 31 subfossil specimens from South Sulawesi. “N_Wear” comprised a discrete indentation or almost circular erosion of the enamel and underlying dentine in a molar tooth; “W_Wear” comprised tooth indentations of irregular shape larger than 7 mm × 7 mm in size; “E_Wear” comprised extensive tooth indentation. “Wear” anomalies were found on 10% of specimens from Buru or the Sula Islands and on 17% of all Sulawesi crania and mandibles. It was hypothesised that tooth grinding of the abrasive seeds of the wild banana (Musa balbisiana Colla) initiated this anomaly. Groove was a deep, oval-shaped cleft cut into the enamel and dentine between two molar teeth. Groove anomalies were evident in 3% of Buru or the Sula Islands specimens and in 12% of all Sulawesi specimens. No conclusion was reached regarding the initiator of the Groove anomaly.