Luopterus

In 2012, pterosaurologists Lü Junchang and Dave Hone described an anurognathid fossil from Hebei, China. It was given the binomial name Dendrorhynchoides mutoudengensis; based on similar shapes of the humerus’s deltopectoral crest, it was referred to the same genus as the earlier-named Dendrorhynchoides curvidentatus. In 2020, however, Hone reviewed the taxonomy of anurognathid pterosaurs and reassigned the species to a new genus, Luopterus. The new genus name, which translates to “Lü’s wing”, honors his co-author on the species’ description, who had sadly passed away by that time. The species name mutoudengensis alludes to Mutoudeng, a town the fossil was found near. The only known specimen is highly crushed and not very well preserved. In spite of this, we can still get a good idea of what Luopterus looked like. It had a wingspan of about 40 cm (16 inches), small for a pterosaur, but the unfused state of several bones indicates it wasn’t fully grown at the time. The skull is crushed, with only the underside visible, but all the skull bones appear to still be present. The skull was wide and bore teeth that were particularly short and robust. These teeth differentiate it from all other anurognathids. Luopterus was originally described as also having longer, recurved teeth, but a re-examination suggests these may simply be shards of other skull bones. The postcranial skeleton is not as well preserved as the skull. The vertebrae of the neck and torso are mostly missing, and some of the limb bones are only partially preserved, or preserved only as impressions. The body was rather standard for an anurognathid, with a short neck, compact torso, and relatively broad wings. The humerus was straight, with a short, triangular deltopectoral crest. As with other anurognathids, the bones in the wing finger do not connect in a straight line, and were able to flex inward like the fingers on our hands. In spite of the preservation quality of the bones, the fossil preserves some soft tissue. Extensive portions of the wing membrane and cruropatagium (the membrane that connects the legs to each other) are preserved, including traces of actinofibrils, and pycnofiber impressions are visible on the right shoulder. The tail of Luopterus was about 85% the length of the femur. This is one of the shortest tails known for a non-pterodactyloid, only beaten by fellow anurognathids Vesperopterylus and Anurognathus. Interestingly, a specimen of another, unnamed anurognathid species discovered near Mutoudeng shows a longer tail, about 150% the length of the femur. This specimen has interlocking rodlike processes that stiffened the tail, an ancestral trait for non-pterodactyloids that isn’t present in any other anurognathid fossils. It appears that the tails of anurognathids became progressively shorter, culminating in Anurognathus with a tail only 50% the length of the femur. Although pterodactyloids also had short tails, they may have evolved independently from anurognathids. Unfortunately, we currently don’t have early anurognathid fossils that would confirm this. The holotype of Luopterus was recovered from the Daohugou Beds of the Tiaojishan Formation, which dates back to the middle Jurassic, about 165 million years ago. It lived alongside an assortment of other pterosaurs, including at least three other anurognathids: Jeholopterus, the aforementioned long-tailed anurognathid, and an unnamed short-tailed anurognathid with branching red pycnofibers. These anurognathids were likely all aerial insect-hawkers. The differences in tooth shape between Luopterus and the other Daohugou anurognathids suggest it may have preferred different prey species than them, avoiding direct competition. Other pterosaurs from the Daohugou beds include the rhamphorhynchids such as Fenghuangopterus and Jianchangnathus, darwinopterans such as Darwinopterus and Pterorhynchus, and the non-pterodactyloid of uncertain relations Daohugoupterus. A rich diversity of arthropods, amphibians, mammals, and paravian dinosaurs rounded out the ecology of the Tiaojishan forests.