Author– Andrew Tucker
Hello there, my name is Andrew. For the last few months, I have had the privilege to assist the Natural History Museum as a Curatorial Assistant, digitising the information of a group of fossil sponges, the lithistids, a polyphyletic group that does not share a common ancestor and, at this moment, is the object of numerous studies. I am also curating the specimens, re-boxing them with new acid-free trays and plastazote foam.
When I read in the news on Wednesday 9 March that the Shackleton Expedition’s ship, the Endurance, had been found I mentioned it to my manager, Senior Curator of Fossil Porifera Collection, Dr. Consuelo Sendino. She recalled that there were fossil sponge specimens gathered by Shackleton in the museum’s collections.
They were not in the part of the collection I was working on, the lithistids, but were archaeocyathids, reef-building sponges that looked like small lop-sided ice cream cones. Now extinct, they first appeared in the Early Cambrian, approx. 521 million years ago and started to decline when the strange Burgess Shale fauna appeared, in the Middle Cambrian, with animals like Anomalocaris, Hallucigenia and the proto-vertebrate Pikaia, an early ancestor of all vertebrate life, including ourselves.
We found the specimens, including one example with a cut and polished side that showed cross sections of the fossil sponges embedded inside a limestone block. It was then when the problems began.
There were plenty of examples of archaeocyathids from Antarctica in the Porifera drawers, but these came from Siberia, Russia, a country which is much in the news of late. However, we will focus on the oldest calcified sponges and not on Russia. Science knows no borders.
We asked for the specimen with a polished side to be photographed while I started writing this blog piece. It was only when I studied the specimen’s label more closely that I found a bigger problem. It clearly stated that this had been collected by a Dr. R. M. Shackleton and presented to the NHM in 1938.
As you might recall, the popular explorer was called Ernest Henry, E. H. and not R.M. and Ernest Henry Shackleton died in 1922. Therefore. it could not have been given to the Museum while he was alive.
I started to search for R.M. Shackleton, just in case R.M. was a child or close relative of Ernest Henry S. who might have made possible a bequest as Shackleton is not a common name and it is the normal procedure for many collections, they are given once the collector passed away.
We searched for this collection in Cleevely’s (1983) World Palaeontological Collections, but we did not find anything. Then, I searched on websites regarding geological studies and I found that R. M. Shackleton was a first cousin once removed of Ernest Henry S. and a well-known geologist in his own right, Doctor Robert Millner Shackleton (1909-2001), whose main area of work was in East Africa, was a lecturer in Geology of our neighbour institution, the Imperial College.
Although nothing is written about his fossil collection the NHM has fossils collected from his geological trips and the specimens we had found were clearly some of these.
So, not the right Shackleton, but I did not want to miss this opportunity to write about these fossil sponges, which reached a diameter mostly between 10 and 25 mm with a proportional height of 80 and 150 mm respectively. The small ones, as those from Siberia, normally have a maximum diameter of 3 mm, but the specimens shown here are much larger.
Archaeocyathids were hypercalcified sponges which inhabited calcareous sea-beds of warm seas, building bioherms like coral do nowadays, in clear warm-tropical or near-tropical seas. This would have been Siberia was located in tropical latitudes and was geographically inverted compared to its present position.
Archaeocyathids made their first appearance in Early Cambrian, in the international Cambrian Stage 2 or the Russian regional stage Tommotian, characterized by the appearance of small shelly fossils called Tommotian fauna after the area of Siberia where they were first discovered, and started their decline in the international Cambrian Stage 4 or the Russian-Kazakhian stage Toyonian. Hence, they lived during 10-15 million years, disappearing in the Middle Cambrian.
Although they have been described as isolated or colonial organisms, nowadays we know they were probably not true colonial organisms, but with a modular organization which conferred them ecological advantages in reef-building settings, such as indeterminate growth leading to larger size, greater powers of regeneration, and the ability to encrust and gain secure attachment to substrates, modularity was one of the main pathways of archaeocyathan evolution.
Modular forms and species with sparsely porous to aporose septa were evidently more frequent in shallower platform areas with greater current activity. In contrast, species with compound outer and inner walls were dominant in deeper environments with gentler ambient currents.
The Archaeocytha Collection at the NHM contains more than 600 specimens, mainly from Antarctica, Australia, Canada, Morocco, Sardinia, Spain and USA. This is one of the richest and most important Archaeocyatha Collections in the world, including a mixture of over 100 cavity slides and thin sections. About a hundred type and figured specimens are present among these specimens (such as Hill, 1965 and Debrenne, 1966).
This collection is a milestone to take into account in order to learn about what are possibly some of the first animals that appeared on our planet.
So, the Shackleton sponges were not collected by Ernest Henry Shackleton, but one of his relatives and have given me the opportunity to show you the first sponges, which appeared more than 521 million years ago in a remote place in Russia.
Moral: Always check your Shackletons!