Showing posts with label marsupial frogs. Show all posts
Showing posts with label marsupial frogs. Show all posts

Monday, June 20, 2011

Aripo Savanna & its Herpetofauna

Trinidad’s Aripo Savanna complex of tropical grasslands, palm islands, marsh forest and moriche palms with numerous slow moving streams, ponds, and puddles. On June 18-19 the Herp Group from the Trinidad and Tobago field Naturalists Club surveyed the herpetofauna. The weather cooperated to a degree with occasional showers and thunderstorms and blistering heat, which creates a very nice sauna-like effect. The TTFNC-HC will summarize the results elsewhere, but here are a few of the highlights.
Rare creatures are sometimes sited on the savanna. Here is Graham White looking 
for them while well camoflaged.

Aripo Savnna 1. The largest remaining remanant of the savanna.

Stevland Charles and Edmund Charles inspect Marsh Forest Vegetation
A Marsh Forest Pond
An Aripo Savanna Sundew.
Leptodactylus fuscus, the most commonly seen and heard amphibian on the Savanna,
The Scorpion Mud Turtle, Kinosternon scorpioides, a savanna and marsh
 forest inhabitat.
The Trinidad Wood Turtle, or Galup, Rhinoclemmys punctularia, another Marsh
Forest - Savanna chelonian.

Predator & prey. The Horse Whip Snake, Oxybelis aeneus and 
 its prey, the Streaked Lizard, Gonatodes vittatus.
A male Hypsiboans punctata (Hylidae) that was calling from this leaf.
The poorly known microhylid frog, Elachistocleis surinamensis
 is quite common  in the Marsh Forest and at the forest edge.

One of the day groups, with Mike Rutherford examining a turtle (middle).

Saturday, February 5, 2011

Re-evolution of Teeth in a Frog

Gastrotheca guentheri
Louis Dollo, a French born, Belgian paleontologist is perhaps best known for supervising the reconstruction of Iguanodon fossils discovered in an underground mine in 1878; and for an idea which says, evolution is not reversible. The idea became known as Dollo’s Law and suggests that once organisms loose a structure during the course of evolution it will not re-evolve. Like most such “laws,” it was doomed to failure due to exceptions. John Wiens, Stony Brook University, has now documented the re-evolution of mandibular teeth in the marsupial frog, Gastrotheca guentheri. It has been long known that frogs do not have teeth on the mandible – with the exception of some frogs of the family Hemiphractidae. Weins used a time-calibrated amphibian phylogeny that demonstrates frogs lost their mandibular teeth 230 million years ago (MYA), only to have Gastrotheca gunetheri (or an ancestor) re-evolve mandibular teeth 5 to 17 MYA. George Kingsley Nobel recognized that Gastrotheca had true teeth, he wrote “The most remarkable osteological feature of the Hemiphractinae is the redevelopment of true teeth on the dentary….Such teeth do not occur in any other Sallientia…”

Weins’ results provide an exceptionally well documented example of re-evolution, demonstrating that mandibular teeth were lost in the ancestor of all living frogs and then re-evolved in the hemiphractid species G. guentheri. Weins points out that the re-evolution of mandibular teeth may not surprise herpetologists, but notes this example has been ignored in the recent literature on Dollo's law. The time involved from the loss of teeth to their re-evolution in Gastrotheca – an absence of at least 225 million years (and probably longer) is remarkable.

For a news story on this article follow this link.

Noble, G. K. 1931The Biology of the Amphibia. McGraw-Hill, New York .

Wiens, J. J. 2011. Re-evolution of lost mandibular teeth ion frogs after more than 200 million years, and re-evaluating Dollo’s law. Evolution, doi: 10.1111/j.1558-5646.2011.01221.x