Shell Fragment Determinations

Dear Nathalie,

The following figures illustrate the shell fragments you found on St. Martins compared to species found in northern South America (particularly Venezuela). Three of the four fragments were Hyriids as you suspected. The fourth is I believe a Mycetopodid. The reason for the lack of the genus Prisodon on my Web page of Venezuela mussels is that I don't believe it really occurrs there. There are currently three recognized genera of winged hyriids found in South America. A paper by Olsson & Wurtz (1951) (which I will send to you) explained and figured how to separate Paxyodon from Prisodon and I offer the short version below:

Family Hyriidae

Genus Paxyodon: Winged shell; SMOOTH exterior surface; anterior lateral teeth well formed and extend OVER and BEYOND the anterior adductor scar.

Genus Prisodon: Winged shell; SMOOTH exterior surface; anterior lateral teeth absent; frilled or fimbriated pseudocardinal teeth extend FORWARD to TOUCH the anterior adductor scar.

Genus Triplodon: Winged shell; pustulated or ROUGH exterior surface; anterior lateral teeth absent; frilled or fimbriated pseudocardinal teeth extend forward to touch the anterior adductor scar.



FIGURE 1a. External views of ANSP 125546 (top) Paxyodon syrmatophorus (Munschen, 1781) from the Orinoco River and HE97-2007C (Bottom) from St. Martin.


FIGURE 1b. Internal views of ANSP 125546 (top) Paxyodon syrmatophorus (Munschen, 1781) from the Orinoco River and HE97-2007C (Bottom) from St. Martin.


FIGURE 2a. External views of HE97-2513B (top) from St. Martin and ANSP 125546 (bottom) Paxyodon syrmatophorus (Munschen, 1781) from the Orinoco River.


FIGURE 2b. Internal views of HE97-2513B (top) from St. Martin and ANSP 125546 (bottom) Paxyodon syrmatophorus (Munschen, 1781) from the Orinoco River.


FIGURE 3a. External views of HE94-873 (top) from St. Martin and ANSP 125546 (bottom) Paxyodon syrmatophorus (Munschen, 1781) from the Orinoco River.


FIGURE 3b. Internal views of HE94-873 (top) from St. Martin and ANSP 125546 (bottom) Paxyodon syrmatophorus (Munschen, 1781) from the Orinoco River.



FIGURE 4a. External views of HE98-2917A (top) from St. Martin and INHS 17032-4 (bottom) Anodontites infossus (Baker, 1930) from the Rio Aroa, near Palma Sola, Yaracuy, Venezuela.


FIGURE 4b. Internal views of HE98-2917A (top) from St. Martin and INHS 17032-4 (bottom) Anodontites infossus (Baker, 1930) from the Rio Aroa, near Palma Sola, Yaracuy, Venezuela.
HE98-2917A: I compared HE98-2917A to all of the edentate or toothless species found in northern South America and I have tentatively identified them Anodontites infossus (Baker 1930). This is a tentative identification because it is very difficult to separate and identify ENTIRE specimens of Anodontities much less shell fragments. The angle of the toothless lateral ridge and the degree to which the umbo projects above the hinge line place it closest to A. infossus. Interestingly enough this species has been found in only one river system (Rio Aroa) on the northern coast of Venezeula (see web site and map).

I would be most interested in your thoughts on how these shells came to be in St. Martins. I have taken slides of all of these in relation to their suspected recent species and will send to you with your specimens.

Kevin