Dynatoaetus

The first fossil remains now identified as belonging to Dynatoaetus were discovered in 1956 and 1969 in Mairs Cave, located in the Flinders Ranges, South Australia. This material included a variety of body parts, including toes, the upper arm and a sternum. The bones, which were found around into the cave, were covered in a thin calcite layer showing that the bones had not been buried and instead preserved simply lying on the floor of the cave. In later years fossils of large raptors were recovered from several more fossil sites across Australia, including Cooper Creek within the Lake Eyre Basin and the Victoria Fossil Cave (both in South Australia), and the Wellington Caves in New South Wales. However it was not until the discovery of 28 additional remains from Mairs Cave, including skull bones and vertebrae, that the various remains were found to have belonged to a single species. The discovery of these remains was made by a group of recreational speleologists and palaeontologists, which entered the cave with the express purpose of finding more fossils of the bird. Many of the bones of Mairs Cave were found to have belonged to a single individual bird, which served as the holotype when the fossils were described as a distinct genus and species by Ellen K. Mather et al. in 2023. Later that same year a second species was described from the Victoria Fossil Cave on the basis of a variety of bones including a humerus, various other limb bones, a quadrate and a partial pelvis. This species, which was noted for being notably smaller than D. gaffae, was named D. pachyosteus. The genus name Dynatoaetus derives from the Ancient Greek "dynatós", a word meaning mighty or powerful, and "āetós" for eagle. ==Species==

• Dynatoaetus gaffae • Dynatoaetus pachyosteus :Dynatoaetus pachyosteus was described the same year as Dynatoaetus gaffae and was noted for being smaller than the type species. Remains of it are currently only known from the Victoria Fossil Cave in South Australia, where fossils of Dynatoaetus gaffae have also been found. The species name is a combination of the Greek "pachys" meaning "thick" or "large" and "osteon", meaning bone. This name reflects the robust bones of this bird. ==Description==

The hindlimbs of Dynatoaetus were robust and much like those of modern eagles, with the femur in particular being described as extremely large and robust. The tarsometatarsus follows the same condition, being robust and large. The metatarsals however are relatively short. Although they too match the other bones in robustness, they are not much different in length from what is observed in female wedge-tailed eagles. The ungual phalanges of Dynatoaetus gaffae, the claws of the toes, are again much larger than those of modern wedge-tailed eagles. The wings are also described as being short and robust. The fossil remains indicate that this eagle was the largest bird of prey to have inhabited Australia, over twice the weight of the extant wedge-tailed eagle. It was, however, not as large as a female Haast's eagle (Hieraaetus moorei) from the same time of New Zealand or Gigantohierax suarezi, a buteonine from Cuba. Unlike these two birds of prey, which both likely obtained their massive sizes due to insular gigantism and a lack of notable competitors, Dynatoaetus was a continental species like the Woodward's Eagle (Amplibuteo woodwardi) from North America. It is therefore believed that its size was at least in part due to its evolutionary history, given that aegypiine vultures are known to regularly obtain large sizes. For instance, Gyps melitensis from the Pleistocene of Malta as well as the Chinese vultures Aegypius jinniushanensis and Torgos sp. were all in a similar size range as Dynatoaetus gaffae. However, due to their much more derived ecology and the influence this had on their morphology, the precise size difference is difficult to determine. Dynatoaetus gaffae may have reached a wingspan of up to while Dynatoaetus pachyosteus was likely comparable in wingspan to the wedge-tailed eagle. Weight estimates were included in the description of the smaller species, Dynatoaetus pachyosteus, with varying results. Estimates based on humerus length yield a mere , but this is deemed to be an underestimate considering the robust nature of the elements. The least circumference of the humerus meanwhile suggests a more expected weight of , while the least circumference of the femur might even support a weight of up to . However, like with humerus length the weight of the femur is likely to be incorrect, as this element often yields overestimates. Dynatoaetus gaffae expectedly yielded higher weight estimates than its relatives, with the least circumference of the tibiotarsus indicating a weight of up to , while the least circumference of the femur, which again likely represents an overestimate, resulted in a weight of up to . Mather and colleagues point out that the large differences among the results is caused by the used algorithms, which are built around a wide variety of vastly different birds. They further highlight that these algorithms generally favour length, not taking into account how weight would be influenced by how robustly built certain birds, like Dynatoaetus, were. They conclude that Dynatoaetus gaffae most likely reached a weight of around , whereas Dynatoaetus pachyosteus would be at least several kilos lighter. ==Phylogeny==

Phylogenetic analysis on the fossil remains of Dynatoaetus used both molecular and morphological data in order to determine its relationship with other birds of prey, resulting in three most parsimonious trees. Nine anatomical characters connect Dynatoaetus to vultures of the subfamily Aegypiinae, however not all of these are unique to the group and may also be found in other birds of prey like some Gypaetinae and Perninae. In the strict consensus tree, it was recovered as the sister taxon to the aegypiine vultures and more basal than Cryptogyps. Together, Dynatoaetus and derived aegypiines clade with the serpent eagles of the subfamily Circaetinae, a group that includes the Philippine eagle. The Bayesian analysis shows similar results, with Dynatoaetus likewise being found in a position basal to modern aegypiines. The key difference is that in this analysis Cryptogyps was not found to be part of this clade and instead a much more basal bird of prey. The phylogenetic analysis conducted following the discovery of Dynatoaetus pachyosteus recover results much the same as the strict consensus of the earlier study. In this study the strict consensus placed both species in a polytomy with the Aegypiinae (including Cryptogyps), while the Bayesian analysis only differed in having the two species actually form a monophyletic clade. Generally, the unique mix of characters seen in Dynatoaetus is thought to be in large part the result of combining phylogenetic traits inherited from its ancestry with morphological traits developed to support its lifestyle, rendering it difficult to determine its precise relationship but confirming its highly distinct nature. Regardless, the relationship between aegypiines and serpent eagles was recovered in all analysis conducted for this species. It could be possible that Dynatoaetus simply diverged from other aegypiine vultures prior to their diversification or that it convergently evolved anatomy similar to serpent eagles due to its predator habits. }} ==Palaeobiology==

Although fossil material of Dynatoaetus is currently limited to the centre and south-east of Australia, specifically South Australia and New South Wales, this may not reflect the raptor's actual range and could instead be simply the result of preservation and collection bias as well as the fact that large predators are inherently rarer than other animals. Mather et al. thus suggest that this bird of prey may have been much more widespread during the Pleistocene. Regardless of its hypothetical range, Dynatoaetus appears to have inhabited a variety of habitats, from the dry inland of Australia to the more temperate coastal regions. Dynatoaetus likely went extinct approximately 50,000 years ago during the late Pleistocene, coinciding with the extinction of much of Australia's endemic megafauna and the disappearance of the scavenging Cryptogyps. It is possible that these extinctions also lead to the rise of the wedge-tailed eagle to the position as apex raptor in Australia, now able to occupy a more generalist niche. ==References==