Introduction to Coecalanth

The living Latimeria chalumnae was first identified off Southern Africa in 1938, and was known from some 200 further specimens all caught off the volcanic islands of the Comoro archipelago near Madagascar until a large female was trawled off Mozambique in August 1991. Further search produced more off Sulewesi  which externally seemed very much the same as L. chalumnae, (Holder et al., 1999) but Inoue and his colleagues (2005) showed that there was a 4.3% difference in nucleotide residues between the Indonesian L. menadoensis and L. chalumnae, thus establishing the two as separate species. Less certainly, they estimated the split between the two to have taken place 20–30 mya, after the collision of India and Eurasia 50 mya.

L. chalumnae and L. menadoensis are (at present) the sole survivors of a specialized crossopterygian group first known from the mid-Devonian. It is much larger (up to 1.6 m) than its forebears, but otherwise very similar to them, covered with large overlapping bony spinous scales, and with the characteristic coelacanth trilobed tail and lobate fins. Like elasmobranchiomorpha, Latimeria uses urea as an osmolyte, and has a rectal gland to excrete Cl-. Recent expeditions to the Comoro islands have successfully used manned submersibles to film Latimeria in its benthic habitat around 200 m. Being neutrally buoyant (the swimbladder is lipid filled) Latimeria drift around slowly near the bottom, sometimes adopting a head-down attitude, and scull about with their paired and unpaired fins seemingly all having independent actions. Despite the lack of intromittent organs, Latimeria bears live young, and the large female caught in a trawl gave birth to 26 young in the trawl. Fossil embryos with yolk sacs are known from the Carboniferous.