| Dahalokely | |
|---|---|
 | |
| Diagram showing known elements | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Superfamily: | †Abelisauroidea |
| Genus: | †Dahalokely Farke & Sertich, 2013 |
| Type species | |
| †Dahalokely tokana Farke & Sertich, 2013 | |
Dahalokely is an extinctgenus of carnivorousabelisauroidtheropoddinosaur from theLate Cretaceous (Turonian) ofMadagascar.
In 2007, during an expedition byAndrew Farke to the north of Madagascar,Joseph Sertich discovered nearAntsiranana the remains of a theropod new to science. In 2010, these were completely excavated by Sertich andLiva Ratsimbaholison. The fossils were then transported to theUnited States of America to be prepared, repaired and scanned in theStony Brook University. After casts had been made and stored in theRaymond M. Alf Museum of Paleontology with inventory number RAM 16010, the original fossils were returned to Madagascar and added to the collection of theUniversity of Antananarivo.[1]
Thetype speciesDahalokely tokana was named by Farke and Sertich in 2013. The generic nameDahalokely means "small thief" inMalagasy, deriving from its estimated length of 3.5 m (11.5 ft) smaller than those of known abelisaurids. Thespecific nametokana means "lonely" in the same language in reference to the isolation of the Madagascansubcontinent. During the Turonian, Madagascar and India were part of the same landmass that had separated from the rest ofGondwana.Dahalokely is the only dinosaur known from Madagascar when the island was separate from Gondwana but still connected with India, formingIndo-Madagascar. In theZooBank the genus has theLife Science Identifier 8147803A-D4BE-4BA9-9701-D853E 37DE411 and the species the LSID AFAE32BB-123A-45D4-B931-4FF2A ABAF41C.[1]
Theholotype,UA 9855, was uncovered in what is informally named theAmbolafotsy Formation, aTuronian-age deposit of the Diego Basin in northern Madagascar, about 93 million years old.[2] It consists of a partial skeleton lacking the skull, of a subadult individual, preserving vertebrae and ribs. These include the fifth neck vertebra, the first, second, sixth, seventh, eighth and ninth dorsal vertebrae, the left dorsal rib, the upper parts of two right ribs, the lower ends of two ribs and some rib fragments. The identification of the position of these elements is tentative. They were not found in articulation but were assumed to represent the same individual as they were discovered not a metre apart.[1]
Initial size estimates ofDahalokely, at 3.5 m (11.5 ft), were based on the assumption it was built like an abelisaurid. Should it have had the more elongated build of the noasaurids, it would have been 4.2–5.6 m (13.8–18.4 ft) long.[1] It was estimated as being 3.8 m (12.5 ft) in length in 2016.[3]
The describing authors established several unique derived traits,autapomorphies. The cervical vertebra has alamina, bone sheet, between the front joint process, theprezygapophysis, and a rear process, theepipophysis, the edge of which lamina is markedly convex, the convex part being longer than the vertebral body and separated from both the prezygapophysis and the epipophysis by conspicuous notches. With the first and second dorsal vertebrae, the prezygapophysis and the lamina between it and the vertebral body are arranged on a vertical line, the joint facet of the prezygapophysis and the front vertebral body face being positioned in the same plane. With the second dorsal vertebra, the joint facets of the rear joint processes, thepostzygapophyses, are strongly concave. From at least the sixth dorsal vertebra onwards, thefossa or hollowed out area, below the prezygapophysis is divided into two smaller depressions.[1]
In 2013Dahalokely was assigned to theAbelisauroidea. The phylogenetic position ofDahalokely among abelisauroids is uncertain. Its vertebrae and ribs have features of both main groups of abelisauroids, theNoasauridae and theAbelisauridae. A phylogenetic analysis published along with its first description foundDahalokely to be a basal noasaurid, but this result was only weakly supported. The incompleteness of the remains and the lack of material that overlaps with known skeletal elements of other abelisauroid species means that the relationships ofDahalokely within the Abelisauroidea are hard to determine.[1] In 2014,Dahalokely was placed as a basal noasaurid.[4]
A phylogeny from 2018 recoveredDahalokely as forming a clade with the Indian abelisauridRahiolisaurus withinmajungasaurinae.[5] Only the phylogenies for Abelisauridae is depicted here.
In the 2021 description ofLlukalkan bothRahiolisaurus andDahalokely were recovered as basalbrachyrostrancarnotaurines.[6]
However, two separate studies from 2018 and 2022 instead recoveredDahalokely as a noasaurid based on their phylogenetic analyses.[7][8]
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