An amphioxus, Branchiostoma sp., was collected during a field trip on the R/V Katy, near Port Aransas, Texas.
The photos I took are not good, so I don't know if a positive ID can be made. It should be in the genus Branchiostoma; I thought it was B. lanceolatum, but in a biotic inventory of the Gulf of Mexico, Chris Cameron did not list the species as occurring in the Gulf. Based on his paper, its distribution and shallow depth (less than 10 m), my best guess is that it represents B. benneti Boschung & Gunter, 1966 (see BioGoMx: http://gulfbase.org/biogomx/biospecies.php?species=Spp-72-0004.
It may be safest to leave it at the genus level. It was the first live amphioxus that I observed. I was surprised at how fast it can swim (for short distances).
Cephalochordata (from Greek: κεφαλή kephalé, "head" and χορδή khordé, "chord") is a chordate subphylum defined by the presence of a notochord that persists throughout life. It is represented in the modern oceans by the lancelets (also known as Amphioxus). Along with its sister phylum Urochordata, Cephalochordata can be classified as belonging to the taxon Protochordata....