Morphology and phylogeny of two acotylean flatworms (Platyhelminthes, Polycladida) from the genera Cryptophallus and Limnoplana in the South China Sea Author Liu, Hai-Long https://orcid.org/0009-0008-4677-0568 Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Guangdong Engineering Research Center for Marine Algal Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China & Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen, China Author He, Bing-Bing https://orcid.org/0009-0008-9323-6050 Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Guangdong Engineering Research Center for Marine Algal Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China Author Li, Shuang-Fei 0000-0002-5045-9165 Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Guangdong Engineering Research Center for Marine Algal Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China Author Wang, An-Tai 0000-0003-4222-9535 Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Guangdong Engineering Research Center for Marine Algal Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China Author Hu, Zhang-Li 0000-0002-2596-8515 Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Guangdong Engineering Research Center for Marine Algal Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China Author Zhang, Yu 0000-0001-7378-6946 Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, Guangdong Engineering Research Center for Marine Algal Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China text ZooKeys 2026 2026-03-30 1275 211 227 journal article 314700 10.3897/zookeys.1275.180665 9fe7accb-ff6a-4657-aeaf-e41a9c835779 EF72FB86-8C8F-4923-ACAF-8DBFE566936F

Table 1. Comparison of morphological characters between species of Cryptophallus.

Species	C. aegypticus	C. eximius	C. sondaicus	C. wahlbergi	C. sinensis sp. nov.	C. japonicus
Body size (mm)	20–65 × 12–35; 62 (mature)	50 × 30 (preserved state)	40 × 20.5	40 × 21	31–25 × 15 (anesthetized state)	40 × 20
Color pattern	uniformly light creamy	uniformly grayish brown	uniformly dark grey- brown without concentration of the median line	uniformly dark brown	grayish brown, darker in the median	Light silvery black, darker in the median
Cerebral eyespots	two scarcely separate clusters	a single cluster	two scarcely separate clusters	a single cluster	two scarcely separate clusters	a single cluster
Tentacular eyespots	6–8, underneath tentacular knobs	about 13	about 20, underneath tentacular knobs	about 13 (Textfig. 12 a) underneath tentacular knobs	5–8, within the tentacular knobs	4–5, underneath tentacular knobs
Mouth	near posterior third of body	anterior part of the body	near posterior fourth of body	near posterior fourth of body	near posterior fourth of body	near posterior third of body
Male and female reproductive anatomy	pv: small, lined with smooth epithelium; ejaculatory duct and prostatic duct open separately at the distal end of penis; rudimentary duct connected with the ductus vaginalis absent	pv: small, lined with smooth epithelium; ejaculatory duct connects to prostatic duct at the distal end of penis; rudimentary duct connected with the ductus vaginalis absent	pv: small, lined with small epithelial folds at its proximal end; ejaculatory duct and prostatic duct open separately at the distal end of penis; rudimentary duct connected with the ductus vaginalis present	pv: relatively large, with a proximally enlarged lumen and lined with small epithelial folds; ejaculatory duct connects to prostatic duct at the distal end of penis; rudimentary duct connected with the ductus vaginalis absent	pv: small, lined with small epithelial folds at its proximal end; ejaculatory duct connects to prostatic duct at the distal end of penis; rudimentary duct connected with the ductus vaginalis absent	pv: small, lined with smooth epithelium; ejaculatory duct connects to prostatic duct at the distal end of penis; rudimentary duct connected with the ductus vaginalis absent
Type locality	Gulf of Suez	Japan	Amboina	South Africa	China	Japan
Reference	Melouk 1940	Kato 1937	Bock 1925	Bock 1913	This study	Kato 1938, 1944