The discovery of fossilized jawbones in Brazil has led to the identification of a novel genus and species of archaic stem tetrapod dating back to the Permian period. This peculiar amphibian relative, christened Tanyka amnicola, possessed laterally oriented teeth and a surface akin to a rasp for grinding, indicating that some ancient four-limbed vertebrates began to incorporate herbivory much earlier than previously theorized by paleontological circles.
Tanyka amnicola. Image credit: Vitor Silva.
Tanyka amnicola inhabited the southern supercontinent of Gondwana during the Early Permian epoch, approximately 275 million years ago.
“Tanyka amnicola originates from an ancestral lineage previously believed to have become extinct much earlier, and it is moreover an exceptionally unusual creature,” stated Dr. Jason Pardo, a paleontologist affiliated with the Field Museum.
“The structure of its jaw exhibits a peculiar torsion that posed significant challenges in our attempts to comprehend its morphology.”
“For years, we grappled with this enigma, speculating whether it represented some form of pathological distortion.”
“However, at this juncture, we have recovered nine specimens of its jaw, all displaying this characteristic twist, including several that are remarkably well-preserved. Therefore, it is not an anomaly but rather an intrinsic feature of the organism’s skeletal architecture.”
Tanyka amnicola represented a stem tetrapod, belonging to the most ancient evolutionary branch of tetrapods, from which two distinct groups eventually diverged – those that reproduced by laying eggs externally on land, and those that oviposited in aquatic environments.
The evolutionary lines leading to contemporary reptiles, birds, and mammals are descended from the lineage that developed watertight eggs suitable for terrestrial incubation; whereas, modern amphibians such as frogs and salamanders are related to those tetrapods whose eggs necessitated constant moisture.
Notwithstanding the divergence of the tetrapod family tree into these new subdivisions, certain stem tetrapods persisted. Tanyka amnicola was one such survivor.
“In its capacity as a surviving member of the stem tetrapod lineage, even after the emergence of more recently evolved tetrapods, Tanyka amnicola bears some resemblance to a platypus. It constituted a living fossil within its temporal context,” observed Dr. Pardo.
Numerous aspects of Tanyka amnicola remain shrouded in uncertainty, most notably its physical form.
“We unearthed these jaws in isolation, and they present a highly anomalous and distinctive morphology,” commented Dr. Ken Angielczyk, a paleomammalogy curator at the Field Museum.
“However, until we discover a jaw articulated with a skull or other skeletal elements unequivocally associated with it, we cannot definitively attribute other recovered bones in its vicinity to Tanyka amnicola.”
Nevertheless, the jawbone of Tanyka amnicola alone sufficed to reveal to the researchers the extraordinary nature of this extinct creature.
“Kindly run your tongue over the teeth located on your lower mandible. Do you perceive how the occlusal surfaces of your teeth are directed superiorly, towards the palate?” the researchers inquired.
“In Tanyka amnicola, the lower jaw was so contorted that, rather than facing upwards, its teeth were oriented laterally, projecting outwards.”
“Concurrently, the portion of its jawbone that, in humans, faces the tongue, was oriented upwards towards the roof of the mouth in Tanyka amnicola.”
“This particular surface of Tanyka amnicola’s jawbone is adorned with a series of minuscule teeth known as denticles, which collectively form a masticatory surface reminiscent of a cheese grater.”
The scientific team has yet to unearth the skeletal components constituting Tanyka amnicola’s upper jaw, but they infer that its superior dentition and denticles were positioned analogously to those of the lower jaw.
“We surmise that the denticles on the lower jaw engaged in abrasive contact with similar dental structures on the superior aspect of the oral cavity,” Dr. Pardo speculated.
“The teeth would have been subjected to mutual rasping, engendering a rather unique methodology for nutrient acquisition.”
Generally, teeth capable of such grinding interactions are employed for the maceration of vegetative matter.
“Based on the characteristics of its dentition, our hypothesis is that Tanyka amnicola was a herbivore, subsisting on plants for at least a portion of its dietary intake,” posited Dr. Juan Carlos Cisneros, a researcher at the Federal University of Piauí.
“It is particularly surprising that a stem tetrapod such as Tanyka amnicola would have developed adaptations for herbivory, given that the vast majority of its contemporary stem tetrapods were exclusively carnivorous.”
The research findings have been published in the esteemed journal Proceedings of the Royal Society B.
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Jason D. Pardo et al. 2026. An aberrant stem tetrapod from the Early Permian of Brazil. Proc Biol Sci 293 (2066): 20252106; doi: 10.1098/rspb.2025.2106
