#diplodocoidea

[new-dinosaurs]

Ardetosaurus viator van der Linden et al., 2024 (new genus and species)

(Neck vertebra of Ardetosaurus viator, with reconstructed portions shaded in white, from van der Linden et al., 2024)

Meaning of name: Ardetosaurus = burnt [in Latin] lizard [in Greek]; viator = traveler [in Latin, referring to the original specimen having been transported from the United States to Switzerland, Germany, and the Netherlands]

Age: Late Jurassic (Kimmeridgian), between 149.21–150.44 million years ago

Where found: Morrison Formation, Wyoming, U.S.A.

How much is known: Partial skeleton of one individual including multiple vertebrae, part of the hips, and some limb bones.

Notes: Ardetosaurus was a diplodocid sauropod, making it a close relative of Diplodocus and Apatosaurus. Given that the type specimen preserves a large portion of the spinal column, it provides valuable information on how the anatomy of the vertebrae varied across different parts of the spine in sauropods. It also exhibits features of the vertebrae that distinguish it from all other known diplodocids.

The type specimen of Ardetosaurus was dug up in 1993–1994 and has been nicknamed "Brösmeli" (meaning "crumbly" in Swiss German). In 2003, part of the specimen, including several of its neck vertebrae, were destroyed by a fire at the Dinosaurier Freilichtmuseum in Germany (hence the name Ardetosaurus), in a case of malicious arson. Based on microscopic examination of its bone structure, the type specimen was an adult at the time of its death, probably about 22 years old.

(Schematic skeletal of Ardetosaurus viator by Ole Zant [scale bar = 1 m], with preserved bones in white and bones that were preserved but subsequently lost in light gray, from van der Linden et al., 2024)

Reference: van der Linden, T.T.P., E. Tschopp, R.B. Sookias, J.J.W. Wallaard, F.M. Holwerda, and A.S. Schulp. 2024. A new diplodocine sauropod from the Morrison Formation, Wyoming, USA. Palaeontologia Electronica 27: 50. doi: 10.26879/1380

[mesozoicmarket]

A dinosaur tooth of a diplodocoid sauropod, possibly Rebbachisaurus garasbae from the Kem Kem Group in Taouz, Morocco. There is more than one morphology present in this deposit, so it is difficult to say which teeth belong to this rebbachisaurid species. Rebbachisaurus was one of the last of the diplodocoids and non-titanosaurian sauropods before the ground goes extinct during the Cenomanian-Turonian boundary event. This species lived alongside currently undescribed titanosaurs.

[confusedhadrosaur]

Day 7: Supersaurus vivianae

[justgoji]

Brachytrachelopan mesai, probably one of the most miserable sauropods in the fossil record.

With Hatsune Miku for scale:

[roygattero]

Brachytrachelopan

Commission for a line-art tattoo design.

Vector illustration.

[alphynix]

Unsolved Paleo Mysteries Month #18 -- The Biggest Beefy Boys

In 1878, during the Bone Wars of American paleontology, Edward Drinker Cope published a description of a partial sauropod vertebra and femur from the Late Jurassic of Colorado (~150 mya). He classified it as a new species of the diplodocoid genus Amphicoelias (which he had named earlier that same year), designating it as Amphicoelias fragillimus in reference to the bone’s poor condition and incredibly fragile structure.

But what set this fragmentary find apart was its sheer size. The partial back vertebra measured around 1.5m tall (5′), with estimates of its full height anywhere up to 2.7m (8′10″) -- twice the size of the same bone in Diplodocus, and far larger than anything else known.

Obviously its very difficult to accurately estimate the full body size of an animal from a single broken bone, but plenty of attempts have been made anyway, producing lengths of up to 60m (197′). For comparison, the largest living animal the blue whale reaches lengths of around 33m (108′).

Around the time of Cope’s death in 1897, his massive fossil collection was sent to the American Museum of Natural History, and the A. fragillimus vertebra was entered into their catalog--

Only to vanish, never to be seen again.

Multiple searches through the collection have found no trace of it, and there’s speculation that at some point the fragile bone may have crumbled entirely into pieces and been thrown away. No other material of A. fragillimus has ever been found in the ~140 years since its description, despite searches of the area where it was originally discovered, leading to claims of the entire specimen being a hoax -- suggestions that Cope exaggerated or typoed his measurements in his rush to outdo his rival Othniel Charles Marsh.

Without that paleontological holy grail of finding the lost fossil or a new specimen, we just don’t know how big that bone truly was, or whether A. fragillimus was a living kaiju or a much more “normal-sized” sauropod. There’s even been some speculation of it being proportioned more like a rebbachisaur, with tall “sailback” vertebrae.

Except...

In a surprise plot twist, there is another.

An absolutely enormous neck vertebra hints at the existence of other gigantic mega-sauropods. We still don’t have enough remains to know what the heck was going on with these animals -- how did they even manage to get so huge? were they rare individuals who lived long enough to grow into “super-adults”? -- but the prospect of perhaps one day finally validating A. fragillimus’ enormous size is exciting.

My version of Amphicoelias fragillimus here works out to about 50m long (164′), although it might be closer to 60m long with a more horizontal neck posture. Its proportions are mainly based on a mixture of Diplodocus, Supersaurus, and Barosaurus, with slightly taller neural spines raising its back profile a bit and some big fat deposits thickening up its tail.

[new-dinosaurs]

Campananeyen fragilissimus Lerzo et al., 2024 (new genus and species)

(Braincase of Campananeyen fragilissimus [scale bar = 5 cm], from Lerzo et al., 2024)

Meaning of name: Campananeyen = Las Campanas air [in Mapudungun]; fragilissimus = the most fragile [in Latin]

Age: Late Cretaceous (Cenomanian)

Where found: Candeleros Formation, Neuquén, Argentina

How much is known: Partial skeleton of one individual including parts of the skull, some vertebrae, the hips, and the feet.

Notes: Campananeyen was a rebbachisaurid, a group of sauropods best known for including the bizarre Nigersaurus from the Early Cretaceous of Niger. The preserved portions of the skull in the Campananeyen type specimen had been previously described in a 2016 paper, but were left unnamed at the time. Like in birds, much of the skeleton in sauropods was hollowed out by a complex network of air sacs extending from their respiratory system. In Campananeyen, this hollowing appears to have been particularly extensive, as it exhibits air spaces in the braincase and hip bones that have not been observed in other rebbachisaurids.

Reference: Lerzo, L.N., F.T. Fernández-Baldor, J.I. Canale, J.A. Whitlock, A. Otero, and P.A. Gallina. 2024. They all floated in the Cretaceous: new rebbachisaurid (Sauropoda, Diplodocoidea) with a highly pneumatized skeleton from the Upper Cretaceous (lower Cenomanian) of Patagonia, Argentina. Historical Biology advance online publication. doi: 10.1080/08912963.2024.2383708

[new-dinosaurs]

Sidersaura marae Lerzo et al., 2024 (new genus and species)

(Partial skull of Sidersaura marae [scale bar = 5 cm], from Lerzo et al., 2024)

Meaning of name: Sidersaura = star [in Latin, referencing the star-like shape of the bony projections under its tail vertebrae] lizard [in Greek]; marae = for Mara Ripoll [director and technician at the Ernesto Bachmann Paleontological Museum]

Age: Late Cretaceous (Cenomanian–Turonian)

Where found: Huincul Formation, Neuquén, Argentina

How much is known: Partial skeletons of two individuals, together including parts of the skull, several vertebrae, and limb bones. A partial fibula (lower leg bone) and a back vertebra representing two other individuals are also known.

Notes: Sidersaura was a rebbachisaurid, a group of sauropods best known for including the bizarre Nigersaurus from the Early Cretaceous of Niger. Sidersaura is one of the youngest rebbachisaurids yet found, as they are not known to have survived past the early Late Cretaceous. Being represented by relatively complete remains, it provides valuable information on rebbachisaurid anatomy, such as confirming the presence of similarities between the tail vertebrae of rebbachisaurids and those of the distantly related titanosaurian sauropods, which has led to members of the two groups being occasionally confused for one another in the past.

Reference: Lerzo, L.N., P.A. Gallina, J.I. Canale, A. Otero, J.L. Carballido, S. Apesteguía, and P.J.Makovicky. 2024. The last of the oldies: a basal rebbachisaurid (Sauropoda, Diplodocoidea) from the early Late Cretaceous (Cenomanian–Turonian) of Patagonia, Argentina. Historical Biology advance online publication. doi: 10.1080/08912963.2023.2297914