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Spicomellus is an extinct genus of ankylosaur that lived in Morocco during the Middle Jurassic.

History[]

Spicomellus were first acquired from a fossil dealer from the United Kingdom in 2019. The locality was retrieved and paleontologists and government officials worked to excavate the site in 2018, not any more material but instead learning more geology. Because of cooperation, a museum is planned to be built in Morocco to house the material recovered from these formations.

Susannah Maidment, Sarah J. Strachan, Driss Ouarhache, Torsten M. Scheyer, Emily E. Brown, Vincent Fernandez, Zerina Johanson, Thomas J. Raven and Paul M. Barrett named S. afer on September 23, 2021.

Description[]

Spicomellus is reconstructed here heavily based on Scelidosaurus based on age. However, it probably looked a lot different in life. Credit: Clumsystiggy on DeviantArt.

Spicomellus is characterized from ribs with fused osteoderms, a feature not seen in any vertebrate. Susannah Maidment et al. (2021) named it. The remains were examined, but nobody had realized what the materials were. Thin histological sections were cut from part of the materials, were the bone structure revealed Spicomellus was an ankylosaur. Of these diagnostic features is a T cross section, which are only observed in thyreophorans, and were fairly confidently identified.

Spicomellus is the first ankylosaur found in Africa, but was also the earliest ankylosaur. Since little are represented by fossils, it is difficult to determine what most of the animal would have looked like. The osteoderms themselves were likely covered by a keratinous sheath. However, it is unknown why this lineage evolved this fusion, whether it were experimentation or an evolutionary one-off. Maidment hopes to search the Morrocan site in the future, in search of more thyreophoran material.

It is only known from a single rib fragment, known as NHMUK PV R37412, and consists of 4 fragments that perfectly fit together. The fused osteoderms would limited mobility. In terms of size and evolutionary relations, it was likely close to Sarcolestes and Tianchisaurus.

Classification[]

Spicomellus may have belonged to a new clade of ankylosaurs, or may have been another type of thyreophoran. However, the fragments S. afer was named from do not allow for testing, so it is currently unknown. It has been suggested to be a basal ankylosaur, and speculated to have diverged early from ankylosaur lineages in Gondwana.

Paleoecology[]

When Spicomellus lived, the modern continents (then conjoined) were separated by water. Most ankylosaurs are from northern Laurasia, with the southern Gondwanan taxa being largely unknown. Gondwanan ankylosaurs are supported by fragmentary remains, but were assumed to have comprised a small portion of the fauna. However, Spicomellus suggests they were more diverse but increasingly rarer than previously assumed.

Spicomellus is known from the El Mers II Formation. It coexisted with the early stegosaur Adraliktit and large sauropods. It fed on low plants and tubers, being hunted by indeterminate theropods, who may have been megalosaurs. The Guettioua Formation was contemporaneous, so it may have also coexisted with some overlapping fauna such as Atlasaurus. The description of S. afer suggests stegosaurs may have went extinct for other reasons.

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