Gryposuchinae is an extinct subfamily of gavialid crocodylians. Gryposuchines lived mainly in the Miocene of South America. However, "Ikanogavialis" papuensis may have survived more recently, into the Late Pleistocene/Holocene. Most were long-snouted coastal forms. The group was named in 2007 and includes genera such as Gryposuchus and Aktiogavialis, although a 2018 study indicates that the group might be paraphyletic and rather an evolutionary grade towards the gharial.
Description
Gryposuchines had long, narrow snouts and protruding eye sockets. One distinguishing feature of the group is the lack of a large exposure of the prootic bone around the trigeminal foramen, a hole in the side of the braincase wall.
Classification
Gryposuchinae was named in 2007 as a subfamily of closely related gavialid crocodilians. It was cladistically defined as a stem-based taxon including Gryposuchus jessei and all crocodilians more closely related to it than to Gavialis gangeticus (the gharial) or Tomistoma schlegelii (the False gharial). The tomistomines (including the living false gharial) were long thought to be classified as crocodiles and not closely related to gavialoids. However, recent molecular studies using DNA sequencing have consistently indicated that the false gharial (Tomistoma) (and by inference other related extinct forms in Tomistominae) actually belong to Gavialoidea (and Gavialidae).
A phylogenetic analysis conducted in the 2007 study found Gryposuchinae to include the genera Aktiogavialis, Gryposuchus, Ikanogavialis, Piscogavialis, and Siquisiquesuchus. The below cladogram is from the 2007 analysis showing the phylogenetic relationships of gryposuchines among gavialoids. Hesperogavialis was excluded due to a lack of skull material, and Dadagavialis due to its 2018 discovery.
Alternatively, phylogenetic studies recovering the tomistomines (including the living false gharial) within Gavialidae have indicated that the members of Gryposuchinae and the genus Gryposuchus may in fact be paraphyletic and rather an evolutionary grade towards Gavialis and the gharial, as shown in the cladogram below:
Paleobiology
The subfamily Gryposuchinae are the sole members of the superfamily Gavialoidea to occupy South America, the duration of which is entirely limited to the Miocene. However, although most of their history is recorded on the continent, dispersion was achieved via a prior presence in the Caribbean (Aktiogavialis, the oldest known gryposuchine, from in the Middle Oligocene of Puerto Rico, and Dadagavialis in the Early Miocene of Panama, respectively). Furthermore, indeterminate gavialoid remains have recovered from the Oligo-Miocene boundary of coastal Brazil. The origin of these gryposuchines is unclear, although traditionally, an African origin has been favoured as gavialids would have been more likely to cross the Atlantic Ocean than the longer expanses of the Pacific Ocean. Moreover, warm equatorial currents run across the Atlantic from Africa to the Americas, assisting in travel.