Well this is an issue that I’ve had cooking up for months and now it’s ready to serve. Not much else to say to be honest so let’s crack in. Later this month we have two requests from @cbishop and @arctika but those will be appearing at the end of the month. And if you want to request an issue on an amazing animal, fabulous fungus, perplexing plant or awesome paleofauna, don’t hesitate to leave a request in the comments.

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Oddity Ark #76 (#256)

Domain: Eukaryota

Kingdom: Animalia

Phylum: Chordata

[Clade]*: Dinosauria

[Clade]*: Theropoda

Family: Carcharodontosauridae

Genus: Acrocanthosaurus

Species: atokensis

*Dinosaurs and some other non-avian archosaurs are currently going through a taxonomic shakeup due to their relationship with modern day birds.

Related Species: Acrocanthosaurus is a Carcharodontosaur, a group of theropod dinosaurs that include species such as Carcharodontosaurus and Giganotosaurus (1).

Range: Acrocanthosaurus remains have been found in fossil bearing rocks of Texas, Oklahoma, Wyoming and Maryland.

IUCN Status: Acrocanthosaurus is extinct and lived in the early Cretaceous period between 113 and 100 million years ago.

High Spined Lizard

Acrocanthosaurus is among the largest of the theropod dinosaurs, reaching a length of up to 11m and a weight of up to six tons. The most notable feature of Acrocanthosaurus’s skeleton are the elongated neural spines on the neck, back and tail vertebrae, which were double the height of the vertebrae they were attached to, resulting in the translation of the species genus name as ‘high spined lizard’. These spines have attachments for muscle, and it is speculated that the structure supported by these spines was used in fat storage, communication with others of its species or in temperature control (2). The ratio of Acrocanthosaurs’s femur in comparison to tibia and metatarsals suggests that the species was not a fast runner, although the prey it was hunting was typically slower moving then the theropod.

Acrocanthosaurus’s skull was long and narrow, with the teeth the typical serrated blade like dentition typical of the Charcodontosaurs. These teeth were suited for slicing flesh off bone unlike the bone crushing teeth found in the unrelated Tyrannosaurs. While short, the arms of Acrocanthosaurus were well muscled and were used to pin prey against its body to reduce the potential to escaoe. Potential prey for Acrocanthosaurus included the ornithopod Tenontosaurus and juvenile and subadult sauropods such as Astrodon and Sauroposideon, although healthy adults, particularly those of Sauroposideon were outside the prey size range of Acrocanthosaurus. Acrocanthosaurus was the largest predator within its range, and likely only faced competition for food resources from others of its own species.

Analysis of bone fragments of Acrocanthosaurus suggests that the species grew slowly and continuously throughout its lifespan, reaching sexual maturity between eighteen and twenty-four years of age (3). Acrocanthosaurus potentially went extinct because of increasing sea levels, particularly the Western Interior Seaway that split the continent of North America in half. As a species associated with fossil beds of floodplain and coastline habitats, Acrocanthosaurus would be at risk from sea-level rises. The niche filled by Acrocanthosaurus would be filled by Tyrannosaurs such as Albertosaurus and Daspletosaurus through the mid-Cretaceous, and Tyrannosaurus rex in the late-Cretaceous.

Family Cladistics #1 – The Carcharodontosauridae Family

The Carcharodontosaurs are a clade of medium to large theropod dinosaurs from the early to mid-Cretaceous period, with some species from the late Jurassic period. The eighteen genera within the Carcaharodontosauridae family all share a few diagnostic features; namely the blade like teeth with serrated edges, swollen protrusions on the skull above the eyes and neural spines on the vertebrae that are at least 1.9 times taller than the base bone they are mounted on. Carcharodontosaurus was the earliest discovered member of the family, being named in 1931, although the fossil material was destroyed during Allied bombing of Germany in the 1940s (4), with fossil material attributed to this species rediscovered in 1995. Alongside Giganotosaurus and Acrocanthosaurus, these three species made up the family Carcaharodontosauridae which contains all species more closely related to Carcharodontosaurus then to Allosaurus.

The oldest members of Carcharodontosauridae hail from Tanzania from approximately 150mya, in the form of Veterupristisaurus (5). The family radiated outwards during the early Cretaceous, with the greatest diversity in South America and Africa, with limited diversity in Europe and Asia, and a single species currently known from North America. The South American species, particularly those in the clade Giganotosaurini, grew very large, with all four species; Giganotosaurus, Mapusaurus, Meraxes and Tyranotitan growing to lengths of 11m or more, comparable with Tyrannosaurs rex, although Carcharodontosaurs are typically lighter than Tyrannosaurs of comparable size. This large size is partially due to large prey size, with Mapusaurys and Meraxes found in bone beds associated with the largest living land animal Argentinosaurus (6).

The Carcharodontosaurs of Europe are smaller than those of Africa and South America but have revealed some interesting developments regarding the family and for theropod dinosaurs as a whole. The forelimbs of Concavenator have structures that resemble of quill knobs, similar to those found in other theropods, suggesting that the species had at least simple feathers (7). Concavenator and the rest of the Carcharodontosaurs are not closely related to the Maniraptorians, a group that includes the Dromaeosaurs, Tyrannosaurs and modern birds among others. The potential presence of feathers on Concavenator suggests that feathers, or the genetic potential to grow feathers, were present in the last common ancestor of the Allosauridae super family and the Maniraptorians.

In fossil beds where Carcharodontosaurs are present, they typically represent the largest carnivores in the area. Where other large predators were present, such as Spinosaurus, which is found in the same fossil beds of Carcharodontosaurus, these predators typically fall into other niches, notably a semi-aquatic predator to avoid competition. The geologically most recent species, Schochilong, found in Ulansuhai Formation of China dating back to 90mya, while small for a Carcharodontosaurid, remained the top carnivore in its environment, and pushes the evolution of large size in tyrannosaurs later into the Cretaceous then previously speculated (8).

References

1. www.arkive.com

2. Harris, Jerald D. (1998). "A reanalysis of Acrocanthosaurus atokensis, its phylogenetic status, and paleobiological implications, based on a new specimen from Texas". New Mexico Museum of Natural History and Science Bulletin. 13: 1–75.

3. D'Emic, Michael; Melstrom, Keegan; Eddy, Drew (2012). "Paleobiology and geographic range of the large-bodied Cretaceous theropod dinosaur Acrocanthosaurus atokensis". Palaeogeography, Palaeoclimatology, Palaeoecology. 333–334: 13–23

4. Smith, Joshua B.; Lamanna, Matthew C.; Mayr, Helmut; Lacovara, Kenneth J. (2006). "New information regarding the holotype of Spinosaurus aegyptiacus Stromer, 1915". Journal of Paleontology. 80 (2): 400–406.

5. Rauhut, Oliver W. M. (2011). "Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania)". Special Papers in Palaeontology. 86: 195–239.

6. Canale, J.I.; Apesteguía, S.; Gallina, P.A.; Mitchell, J.; Smith, N.D.; Cullen, T.M.; Shinya, A.; Haluza, A.; Gianechini, F.A.; Makovicky, P.J. (2022). "New giant carnivorous dinosaur reveals convergent evolutionary trends in theropod arm reduction". Current Biology. 32 (14): 3195–3202.e5.

7. Ortega, F.; Escaso, F.; Sanz, J.L. (2010). "A bizarre, humped Carcharodontosauria (Theropoda) from the Lower Cretaceous of Spain" (PDF). Nature. 467 (7312): 203–206.

8. Brusatte, S.; Benson, R.; Chure, D.; Xu, X.; Sullivan, C.; Hone, D. (2009). "The first definitive carcharodontosaurid (Dinosauria: Theropoda) from Asia and the delayed ascent of tyrannosaurids". Naturwissenschaften. 96 (9): 1051–1058

Picture Credits

1. latest (750×600) (nocookie.net)

2. Acrocanthosaurus_skeleton_(1).jpg (784×454) (wikimedia.org)

3. Cladogram created by Sundown 89, please ask permission before using.

4. Photograph taken by Sundown89, please ask permission before using.

5. R.4336416ece46dd16836edbb75cb81c4c (600×357) (bing.com)

Well there we go, high spined indeed. Next week we have @cbishop’s request to cover, one with a venomous sting in its tail. And if you want to see more amazing animals and plants, please check out the Oddity Arkive or past issues. And if you want even more animals, please check out dearly departed Impurest Cheese’s Guide to Animals which can be found here, or on the blog of the shark toothed @ficopedia

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If you still have a yearning for learning, please check out the master list of Mr Monster’s Martial Arts Journey.