Acanthopholis (/”uh-KAN-tho-FOE-liss”/; “spine-bearing scale” or “thorny scale”) is a genus of nodosaurid ankylosaurian dinosaur that lived during the Late Cretaceous period (Cenomanian stage), approximately 100.5 to 93.9 million years ago. Its fossils have been discovered primarily in England. The name Acanthopholis refers to the bony armor, including spikes and plates, that covered its body. The genus was first named and described by British biologist Thomas Henry Huxley in 1867 based on fragmentary remains.
Description and Classification
Acanthopholis was a quadrupedal, herbivorous dinosaur, meaning it walked on four legs and ate plants. Estimates of its size vary due to the incomplete nature of its fossils, but it is generally thought to have been a medium-sized ankylosaur, possibly reaching lengths of 3 to 5.5 meters (10 to 18 feet) and weighing up to 380 kilograms (approximately 840 pounds). Its body was protected by an arrangement of dermal armor, which consisted of oval, keeled (ridged) bony plates embedded in its skin, along with rows of spikes, particularly prominent around the neck and shoulder region.
Acanthopholis belongs to the order Ornithischia, the group of “bird-hipped” dinosaurs. It is further classified within the suborder Thyreophora, which includes armored dinosaurs like stegosaurs and ankylosaurs. Acanthopholis is considered a member of the family Nodosauridae, a group of ankylosaurs characterized by their armor and the typical absence of a heavy, bony club at the end of their tails, unlike their relatives the ankylosaurids. Other nodosaurids include dinosaurs such as Nodosaurus and Sauropelta. The classification of Acanthopholis has been subject to scientific debate. Due to the fragmentary nature of the original and subsequent fossil finds, some paleontologists consider Acanthopholis a nomen dubium, or “doubtful name,” meaning the available fossils may not be distinct enough to definitively identify it as a unique genus or to fully understand its characteristics and relationships.
Distinguishing Features
Acanthopholis can be identified, albeit with some uncertainty, by several features observable in its fragmentary remains:
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Rows of oval-shaped, keeled dermal scutes (bony plates) forming its protective armor.
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Presence of prominent spikes, likely arranged along its neck, shoulders, and possibly back.
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As a nodosaurid, it would have lacked the bony tail club found in ankylosaurids.
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Relatively small, leaf-shaped teeth, suitable for a herbivorous diet.
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Its skeletal structure, though incomplete, aligns with that of other nodosaurid dinosaurs.
Paleoenvironment and Diet
Fossils of Acanthopholis have been found in the Cambridge Greensand formation in England. During the Cenomanian stage of the Late Cretaceous, this region was a shallow marine environment. The presence of Acanthopholis fossils in these marine sediments suggests that the animals lived in coastal areas or near river systems that flowed into the sea, and their remains were washed out and buried on the seafloor. The climate at this time was generally warm.
As a herbivore, Acanthopholis would have fed on low-growing vegetation. Its small, leaf-shaped teeth were adapted for stripping leaves and other plant material, rather than heavy chewing. Its diet likely consisted of ferns, cycads, and other plants common during the Cretaceous period. It would have browsed on vegetation at or near ground level.
Significance and Ongoing Research
Acanthopholis holds significance as one of the earlier named ankylosaurian dinosaurs from Europe, contributing to the understanding of dinosaur diversity on the continent during the Late Cretaceous. The study of its remains, though challenging, provides insights into the evolution and distribution of nodosaurids. Its fragmentary nature also highlights the difficulties paleontologists face when working with incomplete fossil evidence.
Ongoing research concerning Acanthopholis primarily focuses on:
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Re-evaluating its taxonomic status: Scientists continue to study the known fossil material to determine if Acanthopholis is a valid genus or if its remains should be assigned to other known ankylosaur taxa.
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Comparative anatomy: Detailed comparisons of Acanthopholis fossils with those of other nodosaurids from Europe and North America are undertaken to better understand its evolutionary relationships and specific adaptations.
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Potential discovery of new material: While finds are rare, paleontologists remain hopeful that more complete specimens might be discovered, which could provide clearer information about its anatomy, appearance, and lifestyle, and help solidify its classification.