Spicomellus Temporal range: Middle Jurassic, | |
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Illustration of the holotype. | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | † Ornithischia |
Clade: | † Thyreophora |
Suborder: | † Ankylosauria |
Genus: | † Spicomellus Maidment et al., 2021 |
Species: | †S. afer |
Binomial name | |
†Spicomellus afer Maidment et al., 2021 | |
Spicomellus (meaning "collar of spikes") is an extinct genus of herbivorous ankylosaurian dinosaur that lived in the supercontinent Gondwana during the Middle Jurassic Period. The type and only known species is Spicomellus afer, named and described in 2021. [1] [2] Its remains were found in the third subunit of the El Mers Group (Bathonian-Callovian), near Boulahfa, south of Boulemane, Fès-Meknès, Morocco. [2] The genus name means "spiked collar", from the Latin 'spica' meaning spike, and 'mellum' meaning spiked dog collar and the specific name 'afer' means "the African". [1]
During the Jurassic, eurypodan dinosaurs, in particular stegosaurs, were diverse and abundant in Laurasia (nowadays the northern continents), but their remains are extremely rare in Gondwanan deposits, nowadays the southern continents. Nevertheless, the existence of fragmentary remains and trackways in the deposits of Gondwana indicates the presence of eurypodan taxa there. Spicomellus is the second described eurypodan taxon from North Africa, after Adratiklit , [3] [4] and the oldest known ankylosaur from anywhere in the world, with the possible exception of an unnamed thyreophoran from the Isle of Skye, Scotland that could be up to 2 million years older than Spicomellus, though it is still unknown if this older species was a stegosaur or an ankylosaur. [5] The holotype, NHMUK PV R37412, is housed at the Natural History Museum in London. [1]
It is unknown when the holotype specimen, NHMUK PV R37412, was discovered, but what is known is that it was acquired by the Natural History Museum from a commercial fossil dealer, Moussa Direct, based in Cambridge, U.K. in 2019. [1] Maidment initially believed that the fossil was a forgery, but after CT scanning the fossil, she drew the conclusion that it was a genuine fossil, and Spicomellus afer was described by Maidment et al., on the 23rd of September, 2021 in an article published online in paleontological journal Nature Ecology & Evolution . [1] The holotype of Spicomellus afer consists of a single rib with four co-ossified spines. This is a trait unique to Spicomellus and not known from any other vertebrate. [2] The holotype specimen was histologically sectioned to confirm that it was an ankylosaurian. The information about the locality of the fossil was provided by Direct and confirmed through discussion with the Moroccan fossil dealer who sold it to him. The locality was visited by S.C.R.M. and D.O. in 2019 and 2020, respectively, to study the sedimentology and stratigraphy of the area. They found that the formation consisted of shallow marine and continental mixed clastic, evaporitic and carbonate sediments. [4]
Despite being a basal ankylosaurian, the preserved dermal spikes of the holotype were fused to the bone, which is a trait unique to Spicomellus and not known from any other vertebrate. [2] Because the dermal spikes were fused to the bone instead of being attached to muscle tissue in all other ankylosaurs, this trait would probably have made it harder for the animal to move. [2]
Though its exact size is unknown, it was likely comparable in size to other Middle Jurassic ankylosaurs like Sarcolestes and Tianchiasaurus. [1] This puts our best size estimates for Spicomellus at no longer than 3 metres (9.8 ft) when fully grown.
At first, Susannah Maidment was unsure whether Spicomellus was a stegosaur or an ankylosaur, but Maidment et al. (2021) confirmed that Spicomellus is a basal ankylosaurian. It was probably closely related to the only other known ankylosaurs that were alive at the same time, Sarcolestes and Tianchisaurus. [1] These species come from the U.K. and China, respectively.
Spicomellus is only known from the El Mers Group's El Mers III Formation. It coexisted with the sauropod "Cetiosaurus" mogrebiensis (which may or may not be synonymous with the sauropod Atlasaurus from the contemporaneous terrestrial Guettioua Formation [6] ) and the stegosaur Adratiklit , [4] browsing on low-growing plants and roots and tubers. Predators of the ecosystem consist of indeterminate theropods (possible megalosaurids). [7]
The discovery of Spicomellus also shows that the two major thyreophoran groups (Ankylosauria and Stegosauria) co-existed for over 20 million years, and implies that the extinction of the stegosaurs may have happened for other, still unknown reasons. [1]
Thyreophora is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous.
Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are known to have first appeared in the Middle Jurassic, and persisted until the end of the Cretaceous Period. The two main families of Ankylosaurs, Nodosauridae and Ankylosauridae are primarily known from the Northern Hemisphere, but the more basal Parankylosauria are known from southern Gondwana during the Cretaceous.
Kentrosaurus is a genus of stegosaurid dinosaur from the Late Jurassic in Lindi Region of Tanzania. The type species is K. aethiopicus, named and described by German palaeontologist Edwin Hennig in 1915. Often thought to be a "primitive" member of the Stegosauria, several recent cladistic analyses find it as more derived than many other stegosaurs, and a close relative of Stegosaurus from the North American Morrison Formation within the Stegosauridae.
Polacanthus, deriving its name from the Ancient Greek polys-/πολύς- "many" and akantha/ἄκανθα "thorn" or "prickle", is an early armoured, spiked, plant-eating ankylosaurian dinosaur from the early Cretaceous period of England.
Scelidosaurus is a genus of herbivorous armoured ornithischian dinosaur from the Jurassic of the British Isles.
Paranthodon is a genus of stegosaurian dinosaur that lived in what is now South Africa during the Early Cretaceous, between 139 and 131 million years ago. Discovered in 1845, it was one of the first stegosaurians found. Its only remains, a partial skull, isolated teeth, and fragments of vertebrae, were found in the Kirkwood Formation. British paleontologist Richard Owen initially identified the fragments as those of the pareiasaur Anthodon. After remaining untouched for years in the British Museum of Natural History, the partial skull was identified by South African paleontologist Robert Broom as belonging to a different genus; he named the specimen Palaeoscincus africanus. Several years later, Hungarian paleontologist Franz Nopcsa, unaware of Broom's new name, similarly concluded that it represented a new taxon, and named it Paranthodon owenii. Since Nopcsa's species name was assigned after Broom's, and Broom did not assign a new genus, both names are now synonyms of the current binomial, Paranthodon africanus. The genus name combines the Ancient Greek para (near) with the genus name Anthodon, to represent the initial referral of the remains.
Sarcolestes is an extinct genus of ankylosaurian ornithischian dinosaur from the Oxford Clay of England. The current type and only species is S. leedsi, and the holotype is a single partial left mandible. The genus and species were named in 1893 by Richard Lydekker, who thought they belonged to a theropod.
Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europe, Africa, South America and Asia. Their geographical origins are unclear; the earliest unequivocal stegosaurian, Huayangosaurus taibaii, lived in China.
Huayangosauridae is a family of stegosaurian dinosaurs from the Jurassic of China. The group is defined as all taxa closer to the namesake genus Huayangosaurus than Stegosaurus, and was originally named as the family Huayangosaurinae by Dong Zhiming and colleagues in the description of Huayangosaurus. Huayangosaurinae was originally differentiated by the remaining taxa within Stegosauridae by the presence of teeth in the premaxilla, an antorbital fenestra, and a mandibular fenestra. Huayangosaurinae, known from the Middle Jurassic of the Shaximiao Formation, was proposed to be intermediate between Scelidosaurinae and Stegosaurinae, suggesting that the origins of stegosaurs lay in Asia. Following phylogenetic analyses, Huayangosauridae was expanded to also include the taxon Chungkingosaurus, known from specimens from younger Late Jurassic deposits of the Shaximiao Formation. Huayangosauridae is either the sister taxon to all other stegosaurs, or close to the origin of the clade, with taxa like Gigantspinosaurus or Isaberrysaura outside the Stegosauridae-Huayangosauridae split. Huayangosauridae was formally defined in 2021 by Daniel Madzia and colleagues, who used the previous definitions of all taxa closer to Huayangosaurus taibaii than Stegosaurus stenops, and chose the 2020 phylogeny of Susannah Maidment et al. to illustrate the relationships of the clade:
Dracopelta is a monospecific genus of ankylosaur dinosaur from Portugal that lived during the Late Jurassic in what is now the Lourinhã Formation. The type and only species is Dracopelta zbyszewskii, which is represented by a partial skeleton including unpublished material.
Tatisaurus is a genus of ornithischian dinosaur from the Early Jurassic from the Lower Lufeng Formation in Yunnan Province in China. Little is known as the remains are fragmentary. The type species is T. oehleri.
Loricatosaurus is a Stegosaurid genus from Callovian-age rocks of England and France.
This timeline of stegosaur research is a chronological listing of events in the history of paleontology focused on the stegosaurs, the iconic plate-backed, spike-tailed herbivorous eurypod dinosaurs that predominated during the Jurassic period. The first scientifically documented stegosaur remains were recovered from Early Cretaceous strata in England during the mid-19th century. However, they would not be recognized as a distinct group of dinosaurs until Othniel Charles Marsh described the new genus and species Stegosaurus armatus in 1877, which he regarded as the founding member of the Stegosauria. This new taxon originally included all armored dinosaurs. It was not until 1927 that Alfred Sherwood Romer implemented the modern use of the name Stegosauria as specifically pertaining to the plate-backed and spike-tailed dinosaurs.
The El Mers Group is a geological group in the Middle Atlas of Morocco. It is subdivided into 3 formations named the El Mers 1, 2 and 3 Formations respectively. It is a marine deposit primarily consisting of marl, with gypsum present in the upper part of unit 3. and is the lateral equivalent of the terrestrial Guettioua Sandstone. Dinosaur remains are among the fossils that have been recovered from the group, most notably those of indeterminate theropods, the sauropod "Cetiosaurus" mogrebiensis, the stegosaur Adratiklit, the ankylosaur Spicomellus, the inchnofossil Selenichnites and an indeterminate teleosauroid.
Susannah "Susie" Catherine Rose Maidment is a British palaeontologist at the Natural History Museum, London. She is internationally recognised for her research on ornithischian dinosaur evolution, and was awarded the 2016 Hodson Award of the Palaeontological Association and the 2017 Lyell Fund of the Geological Society of London. She was featured as a 2019 National Geographic Women of Impact.
Adratiklit is an extinct genus of herbivorous stegosaurian dinosaur that lived on the supercontinent Gondwana during the Middle Jurassic period. The genus contains a single species, Adratiklit boulahfa. Its remains were found in the El Mers Group, probably in the El Mers II Formation (Bathonian), near Boulahfa, south of Boulemane, Fès-Meknes, north Morocco.
Parankylosauria is a group of basal ankylosaurian dinosaurs known from the Cretaceous of South America, Antarctica, and Australia. It is thought the group split from other ankylosaurs during the mid-Jurassic period, despite this being unpreserved in the fossil record.
Bashanosaurus is a genus of stegosaur dinosaur recovered from the Bajocian -aged Shaximiao Formation of Yunyang, Chongqing, China. The type species is Bashanosaurus primitivus. It is one of the basalmost stegosaurs and is also the oldest known stegosaur, supplanting the previous oldest known stegosaur, Adratiklit, which is roughly one million years younger.
Jakapil is a genus of basal thyreophoran dinosaur from the Candeleros Formation of Argentina. The type species is Jakapil kaniukura.