Reflectance Transformation Imaging (RTI) is a technique based on multiple digital photos with a fixed camera position and illumination from varying directions. These photos are processed to create an image file in which light source position and reflectance properties can be digitally modified. The method is frequently used in archaeology due to its abilities to visualize surface details. Here we apply RTI imaging to the holotype of the non-pterodactyloid pterosaur Scaphognathus crassirostris from the famous Solnhofen Lithographic Limestone of Late Jurassic age and compare the results with ultraviolet light (UV) imaging. The specimen is of particular historical interest since it was the first pterosaur for which a "fur-like" integument was described, by the German paleontologist and zoologist Georg August Goldfuß in 1831. His publication on this fossil includes detailed paleobiological inferences and culminates in the first published scientific life reconstruction of an extinct vertebrate in its environment. However, soft part preservation was not accepted by later scientists such as Herman von Meyer, and Goldfuß' work on soft part preservation, paleobiology and paleo-art was largely forgotten. With RTI and UV light, pycnofibres covering the neck and the body, as well as aktinofibrils and blood vessels on the wing membrane, were visualized on the Scaphognathus crassirostris specimen, largely confirming Goldfuß' observations. The application of RTI is technically easy and promising for paleontological studies, especially for flat fossils on slabs of sediment, where minor differences in relief might hold crucial information. To our knowledge, this is the first study to apply RTI to soft part preservation in vertebrate fossils.

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In non-mammalian synapsids and early mammals, evolutionary transformations in the feeding and hearing apparatuses are posited to have been prerequisites for the radiation of extant mammals. Unlike most vertebrates, including many early synapsids, mammals have precise dental occlusion, a lower jaw composed of one bone, and middle ear ossicles derived from ancestral jaw bones. We illuminate a related functional transition: therian mammals (eutherians and metatherians) evolved anteriorly directed chewing strokes, which are absent in other synapsid lineages. Anteriorly directed jaw movement during occlusion necessitates anteriorly directed muscle force vectors, and we posit that a shift in muscle orientation is reflected in the fossil record by the evolutionary appearance of a posteriorly positioned angular process in cladotherians (therians and their close kin). Anteriorly directed occlusion might have been absent in earlier synapsids because of the presence of attached middle ear elements in the posterior region of the jaw that prohibited the posterior insertion of jaw musculature. These changes to the masticatory apparatus in cladotherians are likely to have permitted the evolution of novel masticatory movements, including grinding in both the anterior and medial directions (e.g. rodents and ungulates, respectively). Thus, this evolutionary transition might have been a crucial prerequisite for the dietary diversification of therians.

Triconodontidae are considered the first carnivorous crown mammals. A virtual reconstruction of the masticatory cycle in the Late Jurassic Priacodon showed that triconodontid dental function is characterized by precise cutting on elongated crests. The combination of traits linked to both carnivorous diets (e.g. fore-aft cutting edges) and insectivorous diets (transverse crests and lobes) suggests a varied faunivorous diet appropriate to the small body size of most triconodontids. Total length of molar shear decreased with wear, suggesting a dietary shift during ontogeny. Embrasure occlusion is confirmed for P. fruitaensis as indicated by premolar positioning, facet orientation, and collision areas. Embrasure occlusion is considered a general feature of all Eutriconodonta, whereas the previously assumed Morganucodon-like pattern is limited to few early mammaliaforms. Unlike modern carnivores, significant roll of around 10° of the active hemimandible occurred during the power stroke. Roll was likely passive in Triconodontidae in contrast to active roll described for extant therians. The triconodontid molar series was highly uniform and adapted to a precise fit, with self-sharpening lower molar cusps. Whereas the uniformity ensured good cutting capabilities, it likely put the dentition under greater constraints, conserving the highly stereotyped nature of triconodontid molars for 60–85 Ma.

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Abstract An upper “triconodont” molar from the Late Jurassic (late Kimmeridgian) of the Langenberg Quarry in northern Germany is attributed to Storchodon cingulatus gen. et sp. nov. of Morganucodonta. The molar is characterized by continuous lingual and buccal cingula, and a relatively large, buccally-shifted cusp D which is not integrated in the buccal cingulum. With a length of 3.07 mm, the tooth is less than 10 % smaller than the lower holotype molar of Paceyodon davidi, the largest known morganucodontan. The Langenberg morganucodontan possibly represents an example of insular gigantism on an adjacent paleoisland.

Triconodon mordax, from the lowest Cretaceous (Berriasian) part of the Purbeck Group, Dorset, is known by an ontogenetic series of specimens that document aspects of tooth eruption and replacement. Based on micro‐computed tomography of four specimens we refer one mandible to a new species, Triconodon averianovi, which differs from T. mordax in having a more slender, curved c; p4 notably low crowned with slender main cusp and smaller accessory cusps; and molars with weak cingula, m4 being notably smaller with weak cusps a and c. T. mordax is variable in the number of mental foramina and posterior jaw morphology. Scans reveal an earlier developmental stage (p3 in early eruption) than previously recognized for Triconodon, and demonstrate sequential, anteroposterior replacement of premolars; it remains unclear whether p1–2 were replaced. Scans also support an earlier hypothesis that m4 erupted late in life. Onset of m4 mineralization is likely to have coincided with eruption of p3, followed by replacement of dp4 by p4 and eruption of c. The m4 developed within the lingual side of the coronoid process, well above the tooth row. It remained in position and was subsequently accommodated in the active tooth row through unusually prolonged and localized growth of the posterior part of the mandible. This pattern is seen in some later triconodontids and appears to be unique to the family.

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