A small terrestrial vertebrate, engaged in its daily activities eons ago, paused briefly to settle in soft sediment before resuming its journey.
This seemingly insignificant repose, spanning nearly three hundred million years, has now given rise to the planet’s most ancient known fossilized impression of reptilian integument. This remarkable find not only showcases well-defined scales but, astonishingly, what scientific consensus interprets as the creature’s cloaca—a versatile anatomical orifice utilized by numerous species for excretory functions, procreation, and oviposition.
“Such delicate organic structures are exceedingly uncommon within the fossilized strata, and their rarity escalates exponentially the deeper we delve into Earth’s geological epochs,” explains Lorenzo Marchetti, a paleontologist affiliated with the German Natural History Museum in Berlin.
“These vestiges unearthed from the Thuringian Forest offer novel insights into the nascent evolution of reptiles and the development of their dermal coverings.”
Originating from the sedimentary Goldlauter Formation within Germany’s Thuringian Forest Basin, an analytical examination of the deposited impression indicates it was formed by a vertebrate measuring approximately 9 centimeters (or 3.5 inches) in length.
Marchetti and his research cohort have designated this trace fossil as Cabarzichnus pulchrus, signifying a newly identified genus of reptilian resting trace.
Its dimensions, coupled with adjacent pedal impressions, suggest C. pulchrus likely belonged to the Bolosaurian clade, an ancient evolutionary divergence within the reptilian phylum. This organism inhabited the Earth roughly 295 million years ago, during the Asselian epoch of the Early Permian period, a time when reptilian diversity was undergoing accelerated expansion.
The substrate bears a distinct imprint revealing what appear to be ventral scales, structures composed of resilient keratin that function as protective armor. However, the most significant feature resides at the caudal extremity, where modified scales encircle a vent-like aperture—consistent with a cloaca.
This discovery surpasses the previous record-holder, a Psittacosaurus cloaca dated to approximately 120 million years ago, and now represents “the most ancient fossil evidence of a cloacal vent in amniotes,” the investigators articulate in their published work, lending substantial support to established hypotheses regarding the presence of the cloaca in early reptilian forms.
Furthermore, the fossil specimen displays discernible rows of polygonal epidermal scales across its torso, appendages, cranial region, and tail. Their analysis indicates these scales, fabricated from keratin, are analogous to those found in extant reptiles, differing from the more primitive bony dermal coverings.
“Trace fossils transcend mere impressions of locomotion,” Marchetti asserts. “They encapsulate anatomical minutiae that would otherwise be irrevocably lost, playing a pivotal role in enhancing our comprehension of the evolutionary trajectory of early terrestrial vertebrates.”
