On a new genus and species of karst-dwelling freshwater crab (Crustacea, Brachyura, Potamidae) from Peninsular Malaysia Author Tan, Zhi Wan 0000-0002-9878-6958 Department of Biological Sciences, Faculty of Science, National University of Singapore, 16 Science Drive 4, Singapore 117558, Singapore Author Ooi, Qie https://orcid.org/0009-0001-1417-965X Asian Institute of Medicine, Science and Technology University, Jalan Bedong — Semeling, 08100 Bedong, Kedah, Malaysia Author Ng, Peter K. L. 0000-0001-5946-0608 Department of Biological Sciences, Faculty of Science, National University of Singapore, 16 Science Drive 4, Singapore 117558, Singapore & Lee Kong Chian Natural History Museum, Faculty of Science, National University of Singapore, 2 Conservatory Drive, Singapore 117377, Singapore text ZooKeys 2026 2026-04-09 1277 113 136 journal article 314836 10.3897/zookeys.1277.181453 962512ea-480b-4b9b-a09d-7b210e3c4aec 68808D3C-D13A-4071-BCCB-7466AD4BCCD7

Table 1. Morphological differences between Merapohra, new genus, and other similar karst dwelling potamid genera in Southeast Asia.

Morphological character	Merapohra gen. nov.	Cerberusa Holthuis, 1979	Erebusa Yeo & Ng, 1999	Kanpotamon Ng & Naiyanetr, 1993	Nemoron Ng, 1996	Ngan Guinot & Rodríguez Moreno, 2024	Phaibulamon Ng, 1992	Schubartamon Guinot & Rodríguez Moreno, 2024	Terrapotamon Ng, 1986	Thampramon Ng & Vidthanayon, 2013	Tiwaripotamon Bott, 1970
* Original description based on female only.
Carapace	sub-ovate	sub-ovate	sub-ovate	sub-ovate	sub-quadrate	sub-quadrate	sub-quadrate	sub-ovate	sub-ovate	sub-ovate	sub-ovate
Carapace height	low	low	high	low	high	low	low	low	high	low	low
Carapace dorsal surface	mostly smooth, branchial region gently granulose	smooth	mostly smooth, posterolateral margin with granules and striae	smooth	granulose and rugose around anterolateral, gastric, frontal, and postorbital regions	smooth	strongly granulose and rugose throughout	finely granulated throughout	mostly smooth, branchial region gently rugose / granulose	mostly smooth, branchial region gently rugose	smooth
Pterygostomial and sub-hepactic regions	completely smooth	weakly rugose or rugose	smooth to finely granulated	smooth	rugose and granulose	smooth	strongly granulose and rugose	finely granulated	granulose	gently rugose	smooth
Postorbital and epigastric cristae	not well-defined, very weakly granulose	not well-defined, smooth	not well- defined, rounded	well-defined, rugose	well-defined, strongly rugose	defined, as ridges	defined, strongly granulated	not well- defined, rounded	well- defined, rounded with granules	well- defined, sharp	not well-defined, smooth
Anterolateral margin	sub-cristate, very weakly serrated	sub-cristate, smooth	sub-cristate, weakly serrated	cristate, serrated	cristate, serrated	sub-cristate, smooth	cristate, serrated	sub-cristate, weakly serrated	cristate, strongly serrated	cristate, strongly serrated	gently serrated to sub-cristate
Eye stalk	long	short	short	long	long	short	long	short	long	long	long
Mxp 3 exopod	exceeding ischium	exceeding ischium	exceeding ischium	exceeding ischium	not exceeding ischium	exceeding ischium	not exceeding ischium	exceeding ischium	exceeding length of ischium	exceeding length of ischium	exceeding length of ischium
Mxp 3 flagellum	long	absent	long	long	absent	absent	absent	long	long	long	long
Antennular fossa	narrow	broad	broad	broad	broad	broad	broad	broad	narrow	narrow	narrow
G 1 terminal article	broad, strongly recurved upwards distally, with dorsal flap	broad, curving downwards, no dorsal flap	very slender, curving downwards, very small dorsal flap	very broad, gently curving downwards, with bulbous structure on proximal part	broad, gently curving downwards, tall, large hump-like dorsal flap	unknown *	broad, bent outwards 90 °, tip gently recurved, no dorsal flap	unknown *	broad, straight, without dorsal flap	broad, curving downwards, with tall, hump-like, notched dorsal flap	broad, gently recurved distally, with very low or no dorsal flap