Sesarmid Crabs of the genus Geosesarma are found from India and Southeast Asia and the islands of the western Pacific as far east as Hawaii and the Solomons. They are terrestrial of freshwater-dwelling, with egss laid on land; the larvae develop past the free-swiming aquatic stage in the eggs and are similar to the adults when they emerge.
In a paper published in the Raffles Bulletin of Zoology on 9 November 2016, Marivene Manuel-Santos of the Zoology Division at the National Museum of the Philippines, Peter Ng of the Lee Kong Chian Natural History Museum at the National University of Singapore , and Hendrik Freitag of the Biology Department at Ateneo de Manila University, describe two new species of Geosesarma from Palawan Island in the Philippines.
The first new species described is named Geosesarma batak, where 'batak' refers to the Batak people who are indigenous to northeastern Palawan and considered to be the oldest indigenous group in the Philippines. These Crabs have a squarish carapace with the largest male specimen measuring 22.8 by 22.4 mm. They are brown in colour with red and yellow markings. They were found living in forests close to streams, but seldom on the ground, apparently prefering to live in knotholes on trees.
Geosesarma batak, female (20.6 × 20.1 mm), Concepcion, Taranaban River. Manuel-Santos et al. (2016).
The second new species is named Geosesarma tagbanua, after the indigenous Tagbanua people of central and northern Palawan. This species also has a squarish carapace, with the largest male specimen found measuring 21.8 by 21.8 mm. They were found living in a limestone cave and a montane forest in an area with large boulders.
Geosesarma tagbanua, male (21.8 × 21.8 mm), Lipuun Point, Tabon Caves. Manuel-Santos et al. (2016).