Sphenofontis velseraegen. et sp. nov., a new rhynchocephalian from the Late Jurassic of Brunn (Solnhofen Archipelago, southern Germany)

Abstract

The Solnhofen Archipelago is well known for its fossil vertebrates of Late Jurassic age, among which figure numerous rhynchocephalian specimens, representing at least six and up to nine genera. A new taxon, named Sphenofontis velserae gen. et sp. nov., increases rhynchocephalian diversity in the Solnhofen Archipelago and is herein described based on a single, well-preserved specimen originating from the Late Kimmeridgian of the Brunn quarry, near Regensburg. The exquisite preservation of the holotype allowed a detailed description of the animal, revealing a skeletal morphology that includes both plesiomorphic and derived features within rhynchocephalians. Sphenofontis is herein referred to Neosphenodontia and tentatively to sphenodontine sphenodontids. It notably differs from all other rhynchocephalians known from the Jurassic of Europe, showing instead closer resemblance with the Middle Jurassic Cynosphenodon from Mexico and especially the extant Sphenodon. This is evidence for a wide distribution of taxa related to the extant tuatara early in the Mesozoic, and also for the presence of less-specialized rhynchocephalians coexisting with more derived forms during the earliest time in the history of the Solnhofen Archipelago.

Evolutionary origins of the prolonged extant squamate radiation

“…3 . That two thirds of the lepidosaurs from this locality are rhynchocephalians is consistent with previous studies documenting high rhynchocephalian diversity and relative abundance in Triassic-Jurassic lepidosaur faunas 24 – 27 , 90 , in stark contrast to the overwhelming dominance of squamates, and paucity of rhynchocephalians 68 , at middle latitudes in the Northern Hemisphere from the Cretaceous to Recent.…”

An exceptionally preserved Sphenodon-like sphenodontian reveals deep time conservation of the tuatara skeleton and ontogeny

“…Some few exceptions include differences on the anterior end of the snout (e.g., shape of the premaxilla and multiple premaxillary teeth) and the presence of a midventral crest on the vertebrae of N. sani . However, individually recognizable premaxillary teeth instead of a single fused premaxillary tooth were also detected in a recently described sphenodontine ( Sphenofontis ) 21 , thus strongly indicating this was the plesiomorphic condition for sphenodontines, and persisting at least until the end of the Jurassic. Additionally, the morphological changes detected on the upper and lower jaws of N. sani during its ontogenetic development are also very similar to the ontogenetic changes observed in Sphenodon (Fig.…”

“…Until recently, among all sphenodontids, cranial data beyond jaw elements was only available for Sphenotitan , the extant Sphenodon punctatus (among sphenodontines), and for the Late Cretaceous Priosphenodon (among eilenodontines). The recently published Sphenofontis , from the Late Jurassic of Germany 21 has just improved the amount of cranial data available for early sphenodontines, but several aspects of its skull morphology remain unknown pending further preparation or CT scanning. Therefore, the paucity of data for the skull anatomy among early sphenodontines has always imposed a severe constraint on the number of unambiguous synapomorphies recovered for Sphenodontinae, and as a result, the overall number of synapomorphies and support for its sister clade—Eilenodontinae—and internal relationships among early sphenodontids.…”

“…Most notably, there are almost no articulated skulls or postcrania in the fossil record of sphenodontines (but see ref. 21 )—the branch of the sphenodontian tree including Sphenodon , and which is estimated to have originated during the Late Triassic at ~206 Mya 19 . During this 200+ Myr evolutionary history, all fossils robustly assigned to sphenodontines were comprised of jaw elements and isolated vertebrae, including all material referable to taxa such as Cynosphenodon , Kawasphenodon , Sphenovipera , among other unnamed Mesozoic specimens 12 , 14 , 15 , 22 .…”