This small shrew is known from the Lacandona rainforest in Chiapas, southern Mexico. The original description examined two specimens, collected in lowland forest near the archaeological site of Yaxchilán.
The dorsal coat is dark gray to nearly black. In the described specimens, the tail is relatively long compared with the small body.
Cryptotis lacandonensis inhabits humid lowlands around the Usumacinta River on the Mexican–Guatemalan border. It occupies tropical forest rather than the mountain habitats used by many other small-eared shrews.
A 2019 paper reported the first Guatemalan record using a female collected at Bethel in November 1995 and preserved in a university collection. Bethel lies about eighteen kilometres south of the Mexican type locality. The discovery came from re-examining an old specimen, rather than a new capture in 2019.
Researchers extracted and cleaned its skull and measured thirteen cranial features. They compared it with twenty specimens of five other species and published measurements of the two original type specimens. Dental morphology and the measurement analyses together supported identification as Cryptotis lacandonensis. Preserved material supplied new evidence of the distribution across the border.
An extinction-risk assessment has not been added yet.
The 2019 Guatemalan report describes replacement of forest around Bethel by crops and cattle and rapid fragmentation of the species’ original forest, particularly in Guatemala. The authors proposed this shrew as a potential flagship for conservation on both sides of the border and called for further ecological research. Retaining forest and improving knowledge of its distribution and life history are priorities.