The Speculative Dinosaur Project: †Tapejaridae
Today, Spec pterosaur biota is dominated primarily by hastazhdarchine azhdarchids and nyctosaurids, with a few odd clades like carnocursorines and anatochasmines occuring here and there. All these forms belong to two main clades, Pteranodontia and Azhdarchidae, the pterosaurs that seemingly dominated terminal Cretaceous reccords on both worlds, Other pterosaurs, even the closely related clades, were thought to have been disappeared long in the poorly understood extinction events of the mid-Cretaceous, and as such to never have witnessed the start of the Mesozoic. Imagine the specologists’ surprise, then, when they came across the exquisite lagerstattën of the Eocene, such as the Messel Pit. Here, while the familiar Maastrichtian pterosaurs were present, the dominant pterosaurs belonged to another, far unexpected clade, the ever bizarre Tapejaridae.
Tapejarids are part of the same clade of pterosaurs that include the more renowed azhdarchids, Azhdarchoidea, being among the most basal members. Known primarily from the Lower Cretaceous from as far back as the Barremian, their history most likely extends even further back in time, as the earliest known tapejarid, †Europejara, is already a quite derived animal, showcasing the strange jaw anatomy and crests the clade is fabled for. Tapejarids, much like azhdarchids (and the most common contemporary azhdarchoid clade, the chaoyangopterids), seemingly enjoyed a global distribution, with Cretaceous fossils being found in Eurasia, South America and Africa, occuring in a variety of environs from denses forests to scrubby outback. Known from lagerstattën such as the Liaoning complex, many tapejarid fossils offer a good glimpse at pterodactyloid biology, with their pycnofibril pelages, wing membranes, keratinous beaks, crests and claw sheaths and even their mammal-like footpads being well preserved in several specimens.
Tapejarids have long been renowned for their bizarre facial anatomy: unlike other azhdarchids and their usually long and slender beaks, tapejarids have rather short, deep – often made even deeper due to the maxillary and mandible crests – and downcurved bills, resembling in some ways a less robust version of oviraptor maws, though most certainly not adapted for crushing, being far more lightly constructed and lacking the same bite musculature. Deep yet light, these beaks have been compared to those of HE toucans and hornbills and Specworld Scytherbills, suggesting that tapejarids, much like these birds, were frugivorous animals adapted to pick and grab fruits without much effort, though unlike these birds adult animals do not show specialisation towards arboreality, so they would perhaps more often forage by browsing or picking fallen fruits. More impressive yet are their massive crests, with forms like †Tupandactylus/Ingridia having the largest headgear in porportion to the body of any pterosaur, and indeed of any known vertebrate, far exceeding the size of the body. These crests, made almost entirely from soft tissues, have traditionally been interpreted as sails, but are now known to have been keratin-composed, and most likely served a role in sexual selection as with the crests of living Spec pterosaurs. So big were these crests that they might even have been detrimental to the animals’ flight capacities, and perhaps apropriately it seems tapejarids were mostly terrestrial pterosaurs, just like azhdarchids. As to be predicted from their basal position, tapejarids lack many features posterior azhdarchoids have, such as the extreme shortening of the metacarpals I-III, though strangely enough some genera did indeed convergence with more derived azhdarchoids on that aspect, such as †Sinopterus..
Common during the Lower Cretaceous, tapejarids virtually disappear in the post-Cenomanian world, with the exception of the hungarian †Bakonydraco, an unique pterosaur from the Santonian, when azhdarchids already composed most of the terrestrial pterosaur faunas. Part of this disappearence may coincide with the rarity of lagerstattën in the Higher Cretaceous, as indeed tapejarids are almost exclusively found in this type of fossil site, with only the largest forms such as the “Kem-Kem tapejarid” and †Bakonydraco occuring outside of it.
The state of Tapejaridae therefore cannot be accounted for in the Maastrichtian and Paleocene, In Spec’s Eocene, however, these pterosaurs positively thrive: occuring in Europe, North America, Asia, North Africa and Australia (with possible remains from South America and Vega Island), they account for over 70% of all pterosaur fossils, replacing azhdarchids as the dominant pterosaurs in terrestrial settings. While this increase in diversity may be related to the higher amount of konservat-lagerstattën, the presence of tapejarid bones in less radically well preserved fossil environments such as the mongolian Erlian Basin or the Faiyum sites suggests that this was indeed a genuine feature of the Eocene’s pterosaur biotas. In that case, the reasons for such an extreme tapejarid adaptative radiation are poorly understood, but may be related to the global hothouse climate, that favoured environments that these pterosaurs favoured and where azhdarchids were less at home, such as dense rainforests or wetlands.
About six Eocene tapejarid genera are formally named, with several unassigned fossils. Eocene tapejarids are less morphologically diverse than contemporary azhdarchids, perhaps indeed a symptom of the latter’s forced speciation in the face of unfavourable conditions, but nonetheless showcase a wider range of sizes and, as we will later see, facial anatomy. Of the Eocene taxa, the smallest is an as of yet unnamed specimen from the Geiseltal Formation, a seemingly elderly animal with a wingspan of 1.2 meters, while the largest is the impressive †Budorcornis eurasiaticus, at a wingspan of 5 meters, quite possibly the largest volant tapejarid known. The Messel species †Eurodracavis aumalai and †Selenipterosaurus hollandiae also showcasethe extent of pterosaurian superprecociality that would have made tapejarid niche partitioning all the more complex, with fossils of the small, “passerine-like” newborns at wingspans of around 20 centimeters and all the gradual intermeditary stages until the fully grown adults, with wingspans of 2.5 and 3 meters respectively, the most common pterosaur fossils of the pit.
Eocene Spec tapejarids also see a great jaw and crest morphological range. The australian †Namarrana and an undescribed asian taxon both bear un-[bony]crested, long but deep beaks, superficially akin to those of toucans (and like that of the long gone †Sinopterus), while †Eurodracavis bears an uniquely [vertically] triangular rostrum, remaniscent of perhaps the basal condition for Azhdarchoidea, while †Arsinoeavis bears an upturned bill reminiscent of those of HE elephant birds. Most still bear the characteristic deep, short, downcurved jaws, however, though at various levels of depth and length, and with various mandibular crest shapes, from simplemost bumps in several taxa to aq truly impressive “beard crest” in †Budocornis. Messel and Green River taxa have fairly well preserved keratinous headcrests, which seem to follow the classical model, but the african †Arsinoeavis might have bore a truly impressive headgear, as the snout bony crest split into two elongated, thin, curved “horns”; being composed of fine fibrous bone, in life they would have supported two keratinous crests, making it one of the most complicated pterosaurian displaying devices ever known. With the exception of †Eurodracavis, all known Cenozoic tapejarids with well preserved forelimb elements have the same manus condition as neoazhdarchians and pteranodontians, with metacarpals I-III short and having lost contact with the wrist, being locked at the end of the fourth metacarpal.
Tapejarids remained consistently common across the Eocene, but by the Oligocene their number seemingly has decreased radically, with only a few remains known from Europe, North Africa and a possible south american skull. While the Oligocene pterosaur fossil reccord is notoriously poor, azhdarchids once again dominate terrestrial pterosaur faunas, implicating that tapejarids did not enjoy much success with the Oligocene cooling and systematic floral replacement in the global forests. European tapejarids are represented by the genus †Vesperodraco, which might have survived as recently as the late Miocene based on Czech fossil remains. It is possible that the european laurassivalvan forests might had been something of a refuge for these late living Old World tapejarids,and once their systematic disappearence in the late Miocene, these pterosaurs saw themselves in no better condition that the native elphabas and many components of the local avifauna. A few sightings still occur in the Azores, Madeira and Canaries about strange pterosaurs that are often recognised as possible living tapejarids, but most experts believe that they are misidentified hastazhdarchines, particularly Cooper’s Azhdarcho (Hastazhdarcho cooperi).
However, the Cenozoic story of the tapejarids did not end there. Australia’s tapejarids did not seem much affected by the Eocene/Oligocene catastrophies, and remained relatively common, dominating aerial pterosaur faunas (the flightless carnocursorine azhdarchids rose in dominance in the Oligocene). One particular lineage of tapejarids, Brontornithosaurinae, went the same way as their azhdarchid cousins and gave up flight altogether, growing to larger sizes and seemingly occupying a similar ecological niche to that of extinct dromornithids; one particular species, the Miocene-Pliocene †Rhinocerocristatus giganteus, was one of the largest pterosaurs to have ever lived, reaching a weight of roughly one ton and reaching as much as 4.5 meters high. These australian tapejarids remained diverse until the late Miocene, coinciding with the extreme drying of Australia, and the subsequent disappearence of dense rainforests. The larger brontornithosaurines were gradually replaced by the browsing noasaurs, more apt to deal with the tougher vegetation, while volant tapejarids were appearent displaced by bucerosaurine azhdarchids, which became the dominant australian pterosaurs in the late Miocene and Pliocene. The last known brontornithosaurines occured in southeastern Australia in the mid-Pliocene, while volant tapejarids might have disappeared earlier at the Miocene/Pliocene barrier.
While ultimately truly facing oblivion, tapejarids nonetheless are of quite the value for Spec’s scientific research, allowing us to glimpse a window at how Lazarus clades might be able to return to their former glory and beyond, even if for just a short while.