Carliro
patreon
Where and how did pteranodontians come to be?
🕑 Added 2023-12-12 17:13:01 +0000 UTC
Epapetelo by SpinoDragon145
Pteranodontians are a famous clade of Late Cretaceous pterosaurs that include the titular Pteranodon, the nyctosaurs and taxa that sometimes are either pteranodontids or nyctosaurids like Volgadraco. They dominate the Late Cretaceous oceanic environments, seemingly replacing the closely related ornithocheiromorphs and other toothed piscivorous pterosaurs.
Strangely, they appear almost ad nihilo, suddenly bursting into the fossil reccord with no intermediary forms with other pterosaur groups. So, how did these pterosaurs evolve?
In most cladograms, they appear as sister taxa to Ornithocheiromorpha. Seeing as ornithocheiromorphs were around the earliest Cretaceous, this would suggest a ghost lineage of almost 50 million years. Unless early pteranodontians were small aerial insectivores or something, such a ghost lineage appears odd. It may however be corroborated by a Berriasian nyctosaur humerus (Naish et al 2010), assuming it is from a nyctosaur and not from a late surviving rhamphorhynchid (which had similar triangular deltopectorals) or something else entirely.
More likely is that these animals evolved much late and from within the Ornithocheiromorpha, which would make this group paraphyletic in regards to Pteranodontia. After all, both groups are dictated only by morphological traits (the relatively "primitive" ornithocheiromorphs lining together against the "derived" pteranodontians) and there's no way to get genetic analyses. An origin within Ornithocheiromorpha would lessen the degree of the ghost lineage and feel more "natural" than an extended 50 million year ghost lineage.
Within the Ornithocheiromorpha, I find the targaryendraconids to be possible ancestors, sharing upturned jaws with no crests, or alternatively the boreopterids, being freshwater taxa that would have easily survived the Cenomanian mass extinction.
Only further fossils will answer for sure.
