The archaic fauna from New Caledonia
21 September 2011
Our trawls sometimes contain strange organisms, with an ‘out of this world’ morphology.
These unusual shapes can be considered as relicts of a long-gone time. Indeed, some very similar creatures were only known in fossil fauna from the Secondary Era (-150 to -65 million years) and were therefore considered by paleontologists as extinct lineages.
The exploration of deep waters, in particular in New Caledonia, revealed the existence of ‘survivors’ among these lineages that were assumed extinct.
Often referred to as ‘living fossils’ (since the re-discovery of the coelacanth), these organisms possess characters considered as ‘archaic’ in their group because these characters directly link them to fossil fauna.
It is in the upper bathyal zone (200 to 100 m depth) that we found examples of such ‘survivors’.
It is in the upper bathyal zone (200 to 100 m depth) that we found examples of such ‘survivors’. Among echinoderms, and more precisely among the stalked crinoids found in New Caledonia, two are very unusual: Gymnocrinus richeri and Holopus alidis (for more details, see 14 sept 2011 post).
Among crustaceans, two species of attached filter feeding organisms (cirripeds or barnacles) were collected during the ExBoDi cruise: the stalked barnacle Scalpellum sp. and the barnacle Waikalasma boucheti.
Waikalasma possesses a double crown of protective plates, an attribute that is typical of Miocene barnacles from New Zealand (about -35 million years). The first living specimen was collected in Vanuatu during the MUSORSTOM 8 cruise in 1994. We collected it for the first time in New Caledonia, about 500 kilometers farther South.
Among gastropod mollusks, again two examples: the pleurotomaria Perotrochus neocaledonicus, and a Scissurellidae archeogastropod that has not been described yet.
The pleurotomaria group, much enjoyed by shell collectors, is characterized by a deep branchial cleft in Perotrochus.
The Scissurellidae was only known from shells and had never been collected alive. This discovery will allow the detailed description of this very unusual animal and will shed light on its affinities among the family. It was firmly attached to a rock, suggesting it probably feeds on bacterial film. Its flattened shape is especially unusual among the Scissurellidae.
The sponges correspond to one of the oldest zoological groups as it appeared during the early Cambrian, about 570 million years ago. During the ExBoDi cruise, we found some sphinctozoan sponges. This group of calcified sponges, considered as very ‘archaic’, used to form calcareous edifices similar to current coral reefs.
A few days ago, we collected a nice specimen of Vaceletia sp., a genus name dedicated to our spongiologist colleague Jean Vacelet, who first discovered these sphinctozoans in a cave in the Comoros Islands in the 1970’s.
Finally, in a less famous zoological group for the non-biologists, the brachiopods, we found several examples of ‘archaic’ morphology. This group resembles bivalve mollusks but do not belong to mollusks! The species Neoancistocrania norfolki , for example, has a very thick shell. It looks like a stone and is very difficult to pick in the sediments.
Each new research cruise in the waters of New Caledonie confirms that its fauna is extraordinary both for its diversity and for its originality. A true laboratory of evolution, this areas harbors a unique patrimony that needs to be protected.
If you would like to know more
Vacelet, J., J. P. Cuif, et al. (1992). "Un Spongiaire Spinctozoaire colonial apparenté aux constructeurs de récifs triasiques survivant dans le bathyal de Nouvelle-Calédonie." Comptes rendus de l'Académie des sciences. Série 3, Sciences de la vie 314(9): 379-385. fdi:35704
Boisselier-Dubayle, M. C., C. Bonillo, et al. "The phylogenetic position of the 'living fossils' Neoglyphea and Laurentaeglyphea (Decapoda: Glypheidea)." Comptes Rendus Biologies. doi:10.1016/j.crvi.2010.08.007
Laurin, B. (1992). "Découverte d'un squelette de soutien du lophophore de type crura chez un brachiopode inarticulé: description de Néoancistrocrania norfolki gen. sp. nov.(Craniiade)." Comptes rendus de l'Académie des sciences. Série 3, Sciences de la vie 314(8): 343-350. refdoc:5168680
Buckeridge, J. S. (1996). "A living fossil Waikalasma boucheti n. sp.(Cirripedia, Balanomorpha) from Vanuatu (New Hebrides), Southwest Pacific." Bulletin du Muséum national d'histoire naturelle. Section A, Zoologie, biologie et écologie animales 18(3-4): 447-457. refdoc:2530466
Harasewych, M. G. (2002). "Pleurotomarioidean gastropods." Advances in marine biology 42: 237-242, IN231-IN237, 243-294. doi:10.1016/S0065-2881(02)42015-9
