Kronosaurus

The validity of Kronosaurus was a longstanding issue due to the fragmentary nature of the holotype. Welles (1962) declared the taxon as a nomen vanum and recommended the designation of a neotype specimen that would preserve the taxon's validity.[6] McHenry (2009) subsequently proposed that two partial skeletons (QM F18827 and QM F10113) that matched the holotype's features and were from its same geological horizon (Toolebuc Formation) could be candidate neotypes.[7] However, no formal petition to the ICZN to designate a neotype was ever submitted. In 2021, Noè and Gómez-Pérez formally restricted Kronosaurus to the holotype. They subsequently erected a new taxon named Eiectus longmani with the Harvard skeleton (MCZ 1285) as its holotype and reassigned all specimens previously referred as K. queenslandicus to it.[2] This move, which was initially interpreted as renaming the entire species to E. longmani, faced criticism by paleontologists. Darren Naish commented that the apparent renaming was "not a good idea"[8] that discourages stability[9] while paleontologist Daniel Madzia dubbed the situation "Kronogate"[10] and criticized the decision to not petition for a neotype.[11] However, the reassignment of all Kronosaurus material to the new taxon is tentative. Noè & Gómez-Pérez (2021) noted the likelihood that the fossils actually represent multiple pliosaur species, meaning that the Toolebuc Formation specimens could be distinct from E. longmani,[2] and previous studies already suggested that the Harvard skeleton might be distinct from K. queenslandicus.[7]

K. queenslandicus at Harvard University which may have been reconstructed with too many vertebrae

In 1931 the Harvard Museum of Comparative Zoology (MCZ) sent an expedition to Australia for the dual purpose of procuring specimens – the museum being "weak in Australian animals and...desires[ing] to complete its series" – and to engage in "the study of the animals of the region when alive."[12] The Harvard Australian Expedition (1931–1932), as it became known, was a six-man venture led by Harvard Professor William Morton Wheeler, with the others being Dr. P. Jackson Darlington Jr. (a renowned coleopterist),[13][14] Dr. Glover Morrill Allen and his student Ralph Nicholson Ellis,[15] medical officer Dr. Ira M. Dixon, and William E. Schevill (a graduate-student in his twenties and Associate Curator of Invertebrate Palaeontology).[16][12][17] MCZ director Thomas Barbour said at the time "We shall hope for specimens' of the kangaroo, the wombat, the Tasmanian devil and Tasmanian wolf," and the mission was a success with over 300 mammal and thousands of insect specimens returning to the United States.[13][16] Yet Mr. Schevill, the team's fossil enthusiast, remained in Australia after the others had departed and, in the winter of 1932, was told by the rancher R.W.H. Thomas of rocks with something "odd" poking out of them on his property near Hughenden.[5][18][16][19] The rocks were limestone nodules containing the most complete skeleton of Kronosaurus ever discovered.[5][20][21] After dynamiting the nodules out of the ground (and into smaller pieces weighing approximately four tons[22][23]) with the aid of a British migrant trained in the use of explosives,[24] William Schevill had the fossils shipped back to Harvard for examination and preparation. The skull—which matched the holotype jaw fragment of K. queenslandicus—was prepared right away, but time and budget constraints put off restoration of the nearly complete skeleton – most of the bones of which remained unexcavated within the limestone blocks – for 20 years.[20]

K. queenslandicus scale diagram, showing the size of the restored Harvard skeleton along with a more accurate estimate

This interim ended when they came to the attention of Godfrey Lowell Cabot – Boston industrialist, philanthropist, and founder of the Cabot Corporation – "who was then in his nineties" and "had been interested in sea serpents since childhood."[16] Having formerly questioned MCZ director Alfred Romer about the existence and reports of sea serpents, it thus occurred to Dr. Romer to tell Mr. Cabot about the skeleton in the museum closet. Godfrey Cabot thus asked how much a restoration would cost and "Romer, pulling a figure out of the musty air, replied, 'Oh, about $10,000.'" Romer may not have been serious but the philanthropist clearly was because the check for said sum came shortly thereafter.[16][24] Two years – and more than $10,000 – later, following the careful labor of the museum preparators, the restored and mounted skeleton was displayed at Harvard in 1959.[5][20] However, Dr. Romer and MCZ preparator Arnold Lewis confirmed that same year in the institution's journal Breviora that "erosion had destroyed a fair fraction of this once complete and articulated skeleton...so that approximately a third of the specimen as exhibited is plaster restoration."[25] Furthermore, the original (real) bones are also layered in plaster; a fact that, while keeping the fossils safe, makes it difficult for paleontologists to study it – an issue which factors into the controversial question of the true size of the Kronosaurus queenslandicus.[24]

In 2021, a revision of K. boyacensis also transferred most of the remains of K. queenslandicus, including the Harvard remains, to a new genus and species, Eiectus longmani. The revision limits the genus Kronosaurus to the holotype mandible, and treats it as a nomen dubium.[2]

Body-length estimates, largely based on the 1959 Harvard reconstruction, had previously put the total length of Kronosaurus at 12.8 meters (42 ft).[26] However, more recent studies, comparing fossil specimens of Kronosaurus to other pliosaurs suggests that the Harvard reconstruction may have included too many vertebrae, exaggerating the previous estimate, with the true length probably only 9 to 10.9 meters (30 to 36 ft).[4][7] In 2022, the specimens referred to Eiectus longmani were estimated at 10 metres (33 ft) in length and 11 metric tons (12 short tons) in body mass.[27]

Kronosaurus teeth exceed 7 centimeters (2.8 in) in length (the largest up to 30 centimeters (12 in) long with 12 centimeters (4.7 in) crowns). However, they lack carinae (cutting edges) and the distinct trihedral (three facets) of Pliosaurus and Liopleurodon teeth. The combination of large size, conical shape and lack of cutting edges allows for easy identification of Kronosaurus teeth in Cretaceous formations from Australia.[4][31]