Halloween Special X: The legend of a Patagonian Monster

Primo Capri and his Plesiosaur. Photo: Rafael Soriani, 1922

On December 10, 1823, Mary Anning discovered the first complete Plesiosaur skeleton at Lyme Regis in Dorset. Noticed about the oddity of the specimen, George Cuvier wrote to William Conybeare suggesting that the find was a fake produced by combining fossil bones from different animals. But despite their unusual body plan Plesiosaurs were a highly successful group of Mesozoic marine reptiles. Their four limbs are enlarged and modified as propulsive flippers, the trunk is short and stiff, and proportional head size seems to vary inversely with neck length.

The idea of surviving plesiosaurs was popularize in the works of Jules Verne and Sir Arthur Conan Doyle. “The Monster of Lake LaMetrie” (1899), a short story by Wardon Allan Curtis, features an encounter between a scientist and a plesiosaur that has been cast up from the hollow center of Earth.  The modern emergence of the Loch Ness monster in the 1930s was deeply influenced by these stories and films like The Lost World (1925) and King Kong (1933).  Even now, the discovery of fossil remains of plesiosaurs from the freshwater fluvial deposits of the mid-Cretaceous Kem Kem Group of Morocco sparked some sensationalist headlines about the Loch Ness Monster. But a decade before the media frenzy around Nessie, there was an argentinian expedition to hunt a living plesiosaur.

Clemente Onelli (courtesy of Archivo General de la Nación, Argentina). From Brinkman and Vizcaíno, 2014

Clemente Onelli (courtesy of Archivo General de la Nación, Argentina). From Brinkman and Vizcaíno, 2014

It all began in January, 1922, when Martin Sheffield, a flamboyant American hunter and gold prospector living in Patagonia, wrote a letter to Buenos Aires Zoo Director, Clemente Onelli. In the letter, Sheffield claimed that he saw a very strange creature in a lake near Esquel, a small Patagonian town in the foothills of the Andes: “I have been able to see, in the middle of the lake, an enormous animal with a head like a swan and enormous size and the movement in the water makes me suppose a crocodile body.

Sheffield’s account and similar reports from Laguna Epuyén led Onelli to think that the mysterious creature could be a plesiosaur. He organized an expedition to capture the beast alive and bring it back to the zoo in Buenos Aires. Onelli also invited Elmer S. Rigg, an associate curator of palaeontology at the Field Museum of Natural History in Chicago. Riggs, like most of the scientific community utterly discredited that a plesiosaurus was still alived. However, some people took it seriously. That was the case of Dr. Albarracin, President of the Society for the Protection of Animals. He demanded that the Minister for the Interior stop the expedition, under the law 2786, which prohibits the hunting of rare animals.

A report from the Plesiosaur expedition. Scientific American 127: 2

Despite the fail of the expedition, the fever around the plesiosaur did not stop. Primo Capraro, a businessman from Bariloche, used a float with the figure of a plesiosaur making it parade through the streets of the town. Rafael D’Agostino (music) and Amílcar Morbidelli (lyrics) wrote a tango about the creature. And one hundred years later the stories around the monster continued. The last reported sighting was on August, 2020.



Brinkman, Paul & Vizcaíno, Sergio. (2014). Clemente Onelli’s sketch map and his first-hand, retrospective account of an early fossil-hunting expedition along the Río Santa Cruz, southern Patagonia, 1888–1889. Archives of natural history. 41. 326-337. 10.3366/anh.2014.0251.

MATTERS, L., (1922). An antediluvian monster: Is the Argentine Plesiosaurus a fake or a scientific marvel?? Scientific American 127: 2

The enigmatic Scleromochlus and the origin of pterosaurs.

Life reconstruction of Scleromochlus taylori. Image credit: Gabriel Ugueto

Pterosaurs were the first flying vertebrates, and their reign extended to every continent and achieved high levels of morphologic and taxonomic diversity during the Mesozoic. The oldest-known pterosaurs appear in the fossil record about 219 million years ago. Most Triassic pterosaurs are small but already had a highly specialized body plan linked to their ability to fly: shoulder girdle with strongly posteroventrally enlarged coracoid braced with the sternum and laterally facing glenoid fossa; forelimb with pteroid bone and hypertrophied fourth digit supporting a membranous wing; and pelvic girdle with prepubic bone and strongly developed preacetabular process.

Due to the fragile nature of their skeletons and the absence of fossils with transitional morphologies, the origin of pterosaurs is one of the most elusive questions in vertebrate paleontology. In 2020, a study led by Martin Ezcurra demonstrated a close relationship between Lagerpetidae and Pterosauria, and found Scleromochlus as the earliest-diverging pterosauromorph. The recognition of lagerpetids as the sister taxon to pterosaurs provides clues to study the origin of Pterosauria, its specialized body plan and flying abilities.

The newly anatomical features of Scleromochlus taylori. From Foffa et al., 2020.

Scleromochlus taylori, from the early Late Triassic of Scotland, is a tiny reptile with extremely long hindlimbs known from seven largely articulated skeletons on small slabs. It was discovery in 1907 by Arthur Smith Woodward who identified Scleromochlus as a small bipedal running or leaping dinosaur. As early as 1914, Huene interpreted Scleromochlus as an arboreal climbing and leaping pseudosuchian close to the origin of pterosaurs.  A new study led by Dr Davide Foffa support the hypothesis that the first flying reptiles evolved from small, potentially bipedal, cursorial ancestors.

Using microcomputed tomographic techniques, the team led by Dr Davide Foffa, provides new key information of Scleromochlus anatomy. The skull length of Scleromochlus is ~50% of the presacral vertebral column length, as in early pterosaurs; the maxilla has an anterior process that tapers to a point and has a weakly concave anterior margin; the occipital neck is extremely short; the pubis is less than 50% the length of the femur; the femoral head is ‘hook-shaped‘; and the length of metatarsal V is less than half length of metatarsal III.



Foffa, D., Dunne, E.M., Nesbitt, S.J. et al. Scleromochlus and the early evolution of Pterosauromorpha. Nature (2022). https://doi.org/10.1038/s41586-022-05284-x

Ezcurra, M.D., Nesbitt, S.J., Bronzati, M. et al. Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria. Nature (2020). https://doi.org/10.1038/s41586-020-3011-4

Bennett SC.  Reassessment of the Triassic archosauriform Scleromochlus taylori: neither runner nor biped, but hopperPeerJ 8:e8418 (2020) https://doi.org/10.7717/peerj.8418