Evolution

A medical scan reveals the secrets and techniques of New Zealand’s extinct marine reptiles, virtually 150 years after the fossils’ discovery


New Zealand’s fossil file of land dinosaurs is poor, with just some bones, however the assortment of historic extinct marine reptiles is exceptional, together with shark-like mosasaurs and long-necked plesiosaurs.

Plesiosaurs first appeared within the fossil file round 200 million years in the past and died off, alongside dinosaurs, 66 million years in the past.

They’re finest identified for the fanciful however interesting thought, urged by British scientist Sir Peter Scott, that the fabled Loch Ness monster was the truth is a plesiosaur that one way or the other outlasted all different large reptiles and remained undetected all through human historical past.

In a current analysis challenge, we used medical CT imaging to scan plesiosaur fossils collected in New Zealand again in 1872.

The scans reveal a brand new degree of element, confirming that plesiosaurs swam largely with their heads down, in distinction to the Loch Ness creature, and exhibiting a detailed hyperlink between the New Zealand fossils and South American specimens from 70 million years in the past.




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Beds of saurian fossils

In 1872, the Canterbury Museum director Julius von Haast employed self-taught Scottish geologist Alexander McKay to undertake geological surveys and acquire fossils.

Von Haast had heard that explorer and novice scientist Thomas Cockburn-Hood had found important reptile fossils within the higher Waipara Gorge, within the Canterbury area. Cockburn-Hood described the realm as “the saurian beds”, and we now know the marine sediments preserved fossils from 70 million years in the past.

McKay went to the Waipara through the winter of 1872, and he was spectacularly profitable, accumulating a number of partial skeletons of marine reptiles and a whole lot of bones.

Amongst this materials have been two somewhat unimpressive, compressed, semi-spherical groupings of bones. These sat in Canterbury Museum’s storerooms, unidentified and caught contained in the concretions they have been excavated in, for over 120 years.

An artist's impression of an elasmosaur
An artist’s impression of an elasmosaur.
Flickr/Peter Montgomery, CC BY-ND

South American hyperlink

It will take till the late Nineteen Nineties to understand the significance of the fossil. Museum preparator and well-known fossil collector Al Mannering and his colleagues ready these two unloved fossils, chipping away the stone to disclose the bones contained within the rocks.

Visiting English scientist Arthur Cruickshank believed these fossils have been exceptional and presumably much like plesiosaur materials he had seen from South America.

In 2004, Canterbury Museum’s geology curator Norton Hiller and Mannering revealed a paper, through which they urged the 2 teams of bones, the dimensions of soccer balls, have been really the 2 sides of the cranium of the identical animal — one remarkably much like plesiosaurs from South America.




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In 2014, internationally famend marine reptile specialists Rodrigo Otero (Universidad de Chile) and Jose O’Gorman (Argentina’s Museo de La Plata) visited New Zealand and examined the specimens. They concluded Hiller and Mannering have been right. The 2 halves have been certainly from the identical animal and the Waipara fossil was most much like a gaggle of plesiosaurs hitherto solely identified from Chile and Argentina.

They described the Canterbury Museum specimens totally and gave them the scientific title Alexandronectes zealandiensis, Latin for Alexander’s swimmer from Zealandia.

A hospital checkup

Science and know-how transfer on and O’Gorman’s workforce needed to substantiate the evolutionary relationships of Alexandronectes zealandiensis, utilizing the most recent applied sciences.

CT scan images of the skull (left) of  Alexandronectes zealandiensis
CT scan pictures of the cranium (left) of Alexandronectes zealandiensis (the size bar is 40mm).
Jose P. O’Gorman, CC BY-ND

In 2019, I took the 2 fossils to hospital to be CT scanned, utilizing the most recent twin power CT scanners at St George’s radiology in Christchurch. The outcomes have been extraordinary, exhibiting beforehand unseen options of the anatomy.

With out the CT scanning know-how, these particulars may solely have been seen by destroying the fossil. We examined the creature’s inside ear and concluded, based mostly on the orientation of the ear, that it maintained a posture the place its head was habitually held both perpendicular to the physique or simply barely under the physique (not like Loch Ness monster followers would preserve, up within the air like a sock puppet).

We additionally noticed a characteristic referred to as the stapes, additionally unseen in plesiosaurs up till then. The stapes is a small umbrella-shaped bone within the center ear which transmits vibrations from the eardrum to the inside ear.

The reconstructed skull of an elasmosaur, found on Vancouver Island.
The reconstructed cranium of an elasmosaur, discovered on Vancouver Island.
Wikimedia/Roland Tanglao, CC BY-ND

This work allowed us to conclude that Alexandronectes zealandiensis was an uncommon plesiosaur.

It belonged to a novel group of southern-hemisphere plesiosaurs now referred to as the Aristonectinae. This group was a part of the Plesiosaur household referred to as elasmosaurs. They have been the final experiment in plesiosaur evolution, with the longest necks of all plesiosaurs.

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