Cabarzia is an extinct genus of varanopid from the Early Permian of Germany. It contains only a single species, Cabarzia trostheidei, which is based on a well-preserved skeleton found in red beds of the Goldlauter Formation. Cabarzia shared many similarities with Mesenosaurus romeri (a varanopid from Russia), although it did retain some differences, such as more curved claws, a wide ulnare, and muscle scars on its sacral ribs. With long, slender hindlimbs, a narrow body, an elongated tail, and short, thick forelimbs, Cabarzia was likely capable of running bipedally to escape from predators, a behavior shared by some modern lizards. It is the oldest animal known to have adaptations for bipedal locomotion, predating Eudibamus, a bipedal bolosaurid parareptile from the slightly younger Tambach Formation.[1]
Cabarzia is known from a single articulated skeleton, missing only the head, neck, and portions of the shoulder, tail, and left limbs. This holotype specimen, NML-G2017/001, was discovered in 1989 by Frank Trostheide, a fossil collector prospecting at the Cabarz Quarry in the Thuringian Forest of Germany. This quarry preserves a large portion of the Goldlauter Formation, which is a sequence of Early Permian red beds, lake sediments, and volcanic layers slightly older than the nearby Artinskian or Kungurian-age red beds of the Tambach Formation.
Preliminary study of the specimen tentatively considered it an araeoscelidian diapsid reptile, but a 2019 study by Frederik Spindler, Ralf Werneburg, and Jörg W. Schneider reasoned against that assignment after comparing the postcranial anatomy of small Permian amniotes such as basal synapsids, parareptiles, and eureptiles. They argued that it was likely a varanopid closely related to Mesenosaurus, part of the subfamily Mesenosaurinae which they had named the previous year. The specimen was assigned the name Cabarzia trostheidei in honor of both the locale of its collection and its collector.
The dorsal vertebrae have long centra and widely spaced zygapophyses, giving them an hourglass shape when seen from above. Their neural spines are low, rectangular and blade-like. Cabarzia
The forelimb is short and robust relative to the long and slender hindlimb. The humerus in particular is thick, with a large entepicondyle. Cabarzia
The femur is neither particularly robust nor slender, but it does have a thin and angular internal trochanter. Like other varanopids (and diapsids), the tibia and fibula were each relatively long, more than 80% the length of the femur. The ratio of the tibia to the longest toe in the foot (the fourth toe) is 3:4, like Mesenosaurus. The astragalus was large and simple, and the calcaneum abutted it along a slightly concave edge surrounding a narrow hole. The fourth distal tarsal is large and unfused to the fifth distal tarsal. As in Mesenosaurus, the elongated fourth metatarsal had a proximal projection which contacted the short fifth metatarsal. The position of the fossil suggests Cabarzia had a fifth toe which was angled relative to the rest of the foot. One of the most clear differences between Cabarzia and Mesenosaurus was the fact that Mesenosaurus had long but rather straight unguals while those of Cabarzia were shorter, deeper, and sharply curved, a characteristic also known in the hands of Tambacarnifex.
Fused neural spines and well-ossified joints indicate that the holotype specimen of Cabarzia was an adult animal. The curved claws of Cabarzia and Tambacarnifex were likely adapted for predation, in contrast to the more straight claws of Mesenosaurus and Varanops which may have been more useful for digging. The broad ulnare is an adaptation also seen in aquatic animals, although there is no other evidence for aquatic habits in Cabarzia.
Cabarzia