Cabarzia
Cabarzia Temporal range:
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Illustration of the holotype fossil | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Family: | †Varanopidae |
Subfamily: | † Mycterosaurinae
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Genus: | †Cabarzia Spindler, Werneberg, & Schneider, 2019 |
Type species | |
† Cabarzia trostheidei Spindler, Werneberg, & Schneider, 2019
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Cabarzia is an extinct
Discovery
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.[1]
Preliminary study of the specimen tentatively considered it an
Description
The
The forelimb is short and robust relative to the long and slender hindlimb. The
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.[1]
Paleobiology
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.[1]
Cabarzia's proportions (short forelimbs, thin body, long hindlimbs and tail) are similar to those of modern lizards capable of bipedalism. They also match the Tambach bolosaurid Eudibamus, although the 'sprawling" ankle and foot of Cabarzia are not as specialized for bipedal habits. This may indicate that Cabarzia did not engage in active bipedalism (slow, methodical walking on the hindlimbs) but rather passive bipedalism (a shift into a bipedal posture when running at high speeds, due to the center of weight being behind the hindlimbs). The advantage of passive bipedalism is not fully understood, even in living reptiles, though it may be involved with increased coordination or assistance in the capture of flying insects. Other "mesenosaurines" (such as Mesenosaurus) shared Cabarzia's adaptations for bipedalism, and may have had increased hip musculature to habituate to the lifestyle further. Information on "mesenosaurine" foot proportions afforded by the description of Cabarzia indicates that they are good candidates for the trackmakers of Dromopus, a common Permian reptile footprint ichnogenus which has traditionally been assumed to have been created by araeoscelidian diapsids. Although no known Dromopus fossils seem to correspond to bipedal animals, this is likely due to bipedalism in "mesenosaurines" being restricted to rare circumstances where they are forced to escape predators. As Cabarzia is the oldest known "mesenosaurine" and predates the previously oldest known bipedal animal (Eudibamus) in Thuringian stratigraphy, Cabarzia can be considered the oldest animal known to have practiced bipedalism.[1]
References
- ^ S2CID 91871872.