Toxicofera
The Toxicofera (Greek τοξίνη, toxine = "poison", Latin ferre = "to carry") are a taxon (a systematic group) of the pangolins (Squamata). It includes the snakes (Serpentes), the creepers (Anguimorpha) and the iguanas (Iguania).
The relationship of these three externally distinct groups is based on molecular biological studies and supported by only a few morphological characters. According to the phylogenetic tree of the pangolins based on molecular biological data, the creepers and the iguanas are sister groups, the unnamed clade formed by both taxa is the sister group of the snakes.
Up to now, only the poisonous snakes (Elapidae), the vipers (Viperidae), and the mantis snakes, as well as the creeping lizards (Heloderma), which belong to the creeping species, were considered to be poisonous scaled creepers. Therefore, an independent origin of this trait at least twice in squamate evolution was assumed. The Toxicofera concept, on the other hand, assumes that the ability to produce toxins evolved only once during phylogeny. The common ancestor of all Toxicofera is thought to have lived about 230 to 200 million years ago in the Upper Triassic.
Meanwhile, venom-producing glandular tissue has also been found in the upper and lower jaws of an iguana-like species, the Eastern bearded dragon (Pogona barbata). In addition, symptoms that occur after bites from Komodo dragons, variegated dragons and banded tree dragons (which belong to the creeping dragon family) are no longer interpreted as the result of bacterial infection alone, but as the result of active venom secretion. In the meantime, venom glands in the mandibles of the Komodo dragon have been detected with the help of 3D scans of a skull in a magnetic resonance tomograph. There is also evidence of the presence of venom glands in Upper Cretaceous fossil creepers.
Today, about 4600 species of the 7900 species of pangolins, or about 58 percent, belong to Toxicofera.
Cladogram of Toxicofera:
Questions and Answers
Q: What is Toxicofera?
A: Toxicofera is a hypothetical clade of Squamata, specifically comprising of all venomous reptile species, as well as related non-venomous species.
Q: What does Toxicofera mean?
A: Toxicofera means "those who carry toxins" in Greek or Latin.
Q: How many living species are included in Toxicofera?
A: About 4600 living species are included in Toxicofera.
Q: What is the significance of Toxicofera?
A: The significance of Toxicofera lies in the fact that it was identified when research showed that the evolution of venom was very ancient and that it might have occurred only once.
Q: What is the difference between venomous and non-venomous species in Toxicofera?
A: Venomous species in Toxicofera have the ability to produce and deliver toxin or venom, while non-venomous species lack this ability.
Q: What is a clade?
A: A clade is a group of organisms that includes a common ancestor and all descendants of that ancestor.
Q: How did researchers identify Toxicofera?
A: Researchers identified Toxicofera when they found evidence that the evolution of venom was a very ancient occurrence and that it might have only happened once, thus placing all venomous and related non-venomous species in the same clade.
