Ainsworth’s Salamander

Last seen in 1964: Plethodon ainsworthi, sp. nov.

Ainsworth’s Salamander is known only from two specimens collected by biologist Jackson Harold Ainsworth in 1964, two miles south of Bay Springs in Jasper County, Mississippi. Ainsworth assumed that the two individuals were Slimy Salamanders (Plethodon glutinosus). More than 30 years later, however, American herpetologist James Lazell described the salamanders found by Ainsworth as a new species, P. ainsworthi.

Lazell’s scientific first description (1998) indicates that Ainsworth’s Salamander was black-brown and showed no particular pattern. The belly of the slender animal was light grayish-brown. The type specimens had a total length of approximately 5.2 and 5.7 centimeters.

Despite intensive searches in 1991, 1995, and 1997, Ainsworth’s Salamander, which belongs to the genus of woodland salamanders (Plethodon), could not be rediscovered. The International Union for Conservation of Nature (IUCN) therefore declared it extinct in 2004.

The IUCN considers increasing deforestation and the associated loss of habitat as the cause of the species’ disappearance. Soil erosion and the drying up of springs may also have contributed to the extinction of Ainsworth’s Salamander. As an amphibian, it inhabited both terrestrial areas and freshwater.

The IUCN lists Ainsworth’s Salamander as the only extinct amphibian in the USA. In the 1980s, the Jalpa False Brook Salamander, endemic to Guatemala, also disappeared. And the El Empalme Worm Salamander (Oedipina paucidentata) from the island of Costa Rica was last sighted in 1952.

Ainsworth’s Salamander – Profile

Alternative name	Bay Springs salamander
Scientific name	Plethodon ainsworthi
Original distribution area	Mississippi (USA)
Time of extinction	approx. 1964
Causes of extinction	Habitat loss, soil erosion, drying up of springs
IUCN status	extinct

Ainsworth’s Salamander: Extinct, Extant, or Nonexistent?

The fact that Ainsworth’s Salamander could not be found despite multiple search efforts may not be due to the species’ extinction at all. The two biologists John G. Hilmes and David C. Beckett also visited the site in 2000 and 2001 where Jackson Harold Ainsworth had found two animals in 1964. There, they also encountered no Ainsworth’s Salamander, but plenty of Mississippi Slimy Salamanders (Plethodon mississippi).

In a study published in the Southeastern Naturalist in 2013, Hilmes and Beckett investigate the question of whether Ainsworth’s Salamander is even a valid species. Rather, they suspect that Plethodon ainsworthi is a junior synonym for the syntopic Plethodon mississippi, or the Mississippi Slimy Salamander.

Hilmes and Beckett assume that Lazell’s scientific first description of Ainsworth’s Salamander may have been influenced by the fact that the type and paratype were presumably stored in strong formalin for 26 years before their determination in 1998. They were therefore already in poor condition.

According to Lazell’s first description, Ainsworth’s Salamander is said to differ from the Mississippi Slimy Salamander by shorter limbs and a noticeably more attenuated body. However, Hilmes and Beckett view the alleged differences between the two species as a consequence of the long-term, improper preservation of the specimens. This leads them to assume that Ainsworth’s Salamander is not a distinct species, but rather the Mississippi Slimy Salamander.

Preservation damage: Characteristic features barely discernible

Of the two specimens of Ainsworth’s Salamander, already damaged by preservation, only the holotype remains today. It has broken into various pieces due to the strong formalin. The left foreleg, the tail end, all toes on the hind legs, and the first toe on the right foreleg are broken off.

The paratype was severely damaged and almost destroyed during a vertebral bone examination. The bones were completely decalcified due to long immersion in formalin. However, the specimen could be photographed and analyzed before the unsuccessful examination.

In 2020, herpetologist Todd W. Pierson and his colleagues presented a study in the Journal of Herpetology on morphological changes in salamanders caused by preservation. They investigated the influence of preservation methods on morphological measurements. The results of their investigation make the scientists doubt Hilmes and Beckett’s hypothesis that the Ainsworth’s Salamander specimens are actually poorly preserved Mississippi Slimy Salamander specimens.

Pierson’s attempts to extract DNA from the decades-old Ainsworth’s Salamander holotype failed, so he could not prove the opposite. Furthermore, the demineralization of the Ainsworth’s Salamander skeleton makes skeletal comparisons impossible. Pierson and his colleagues ultimately recommend continuing to recognize Plethodon ainsworthi as a valid, but probably extinct, species.