Cebudonus poppeorum, a new genus and new species of eumedonine crab (Crustacea: Decapoda: Brachyura: Pilumnidae) from the Philippines Author Ng, Peter K. L. text Zootaxa 2014 3815 1 94 102 journal article 45505 10.11646/zootaxa.3815.1.6 963ff3a4-4ab4-495b-95eb-a744279bc6a4 1175-5326 226599 51A13505-C327-49F7-8FCC-0C407927C76C Cebudonus n. gen. Type species . Cebudonus poppeorum n. gen. , n. sp. , by present designation. Diagnosis . Carapace pentagonal; dorsal surface gently convex, covered with numerous small pits ( Figs. 1 , 2 ); front with 2 long pseudorostral spines, subparallel, ca. 0.4 times total carapace length, separated by broad U-shaped cleft ( Figs. 1 , 2 , 3 C); anterolateral margin entire, with large, broadly triangular, sharp lateral tooth, projecting laterally, dorsal surface gently convex ( Figs. 1 , 2 , 3 A, 4A); antennae with subrectangular basal article, twice as long as wide ( Fig. 3 B); antennules folding at ca. 45° ( Fig. 3 B); epistome relatively broad with depressed median part ( Fig. 3 A–C); third maxilliped with ischium subrectangular, with deep submedian longitudinal sulcus ( Figs. 3 C, 4A), merus subquadrate, anteroexternal angle subauriculiform ( Figs. 3 C, 4A); ambulatory legs long, slender ( Figs. 1 , 2 , 4 E); ambulatory merus elongated, slender, surface with margins rounded, not cristate, not distinctly granular, dorsal distal tooth distinct but low ( Figs. 1 , 2 , 4 E); ambulatory propodus, dactylus with ventral margins lined with dense stiff setae, with distinct dactylo-propodal lock, not forming subchelate structure ( Figs. 1 , 2 , 4 D, E); cheliped merus rounded in cross-section; surface covered with numerous small pits ( Figs. 1 , 2 , 3 C); cheliped carpus surface with long, gently curved spine on distal inner angle ( Figs. 1 , 2 , 3 F); chela unarmed, margins not cristate ( Fig. 3 F); thoracic sternum relatively narrow transversely, surfaces pitted, sternites 3, 4 completely fused with median depression ( Figs. 3 C, 4B); male abdominal locking mechanism present as knob-like tubercle on distal one-third of thoracic sternite 5; male abdomen broadly triangular ( Figs. 3 D, 4C); G1 slender, sinuous, distal part elongated ( Fig. 4 F, G). Etymology . The new genus is named after Cebu City in the Visayas, Philippines ; in arbitrary combination with the genus name Eumedonus . The gender of the genus is masculine. Remarks . The unusual combination of carapace, cheliped, ambulatory leg, thoracic sternal and abdominal characters in Cebudonus poppeorum n. gen. , n. sp. require the establishment of a new genus. While the carapace shape of Cebudonus n. gen. superficially resembles species associated with echinoids like Eumedonus intermedius Chia & Ng, 2000 ( Madagascar ) , E. vicinus Rathbun, 1918 ( Australia ) , and E. zebra Alcock 1895 (Red Sea to East China Sea), especially with regard to the shape of the laterally directed spines; its front is completely different, with two long pseudorostral spines ( Figs. 1 , 2 ) in contrast to Eumedonus , which has a lobiform pseudorostrum that is bifurcated distally to form two teeth (cf. Chia & Ng 2000 : figs. 8, 9A, D, 10, 11, 12A, D, N, 13, 14, 15A, D, Q, R). The lateral carapace tooth and the dorsal surface adjacent to it is gently convex dorsally in Cebudonus n. gen. ( Fig. 3 A) (the tooth is stout with the dorsal surface distinctly convex in Eumedonus ; cf. Chia et al. 1995: fig. 3A); the cheliped merus is relatively long and unarmed ( Figs. 1 , 2 , 3 C) (relatively short with numerous tubercles and granules in Eumedonus ; cf. Chia & Ng 2000 : figs. 8, 9B, 10, 11, 12B, L, 14, 15B, O); the meri of the ambulatory legs are long, subcylindrical and smooth, without any marginal cristae, and the dorsal distal tooth is relatively low ( Figs. 1 , 2 , 4 E) (short, laterally flattened with distinct marginal cristae and a strong dorsal distal tooth in Eumedonus ; cf. Chia & Ng 2000 : figs. 8, 9E, G, 10, 11, 12E, K, 13, 14, 15E, K); the anterior male thoracic sternum (sternites 1–4) are proportionately narrow transversely ( Figs. 3 C, 4B) (proportionately wider transversely in Eumedonus ; cf. Chia & Ng 2000 : figs. 9C, 11B, 12C, 14B, 15N); and the male abdomen is relatively wide ( Figs. 3 D, 4C) (proportionately narrower in Eumedonus ; cf. Chia & Ng 2000 : figs. 12J, 14J, 15N). The unarmed and non-cristate ambulatory meri of Cebudonus n. gen. resembles that of the echinoid symbiont Gonatonotus , but in the new taxon, it is proportionately much longer, more slender and almost smooth ( Figs. 1 , 2 , 4 E) (proportionately shorter and distinctly granular in Gonatonotus ; cf. Chia & Ng 2000 : figs. 17, 18E, G, 20, 21E, K, 22, 23E, K). The differences previously noted in the form of the front, anterolateral region, cheliped, thoracic sternum and abdomen between Cebudonus n. gen. and Eumedonus also apply for Gonatonotus (cf. Chia & Ng 2000 : figs. 17, 18A, D, 19A, 20, 21A, D, M, N, 22, 23A, D [front]; figs. 17, 18B, 20, 21B, 22, 23B [chelipeds]; figs. 17B, 19G, 20B, 21C, 22B, 23C [sternum]; figs. 19H, 21J, 22, 23J [abdomen]). The form of the front, with the two long pseudorostral spines is similar to that of Tiaramedon and Zebrida , but these genera differ markedly from Cebudonus n. gen. in several other characters. Cebudonus n. gen. , can be separated from Tiaramedon by its smooth dorsal surface of the carapace ( Figs. 1 , 2 ) (armed with additional gastric and branchial spines in Tiaramedon ; cf Chia & Ng 1998 : figs. 7A, 8A); the two pseudorostral spines joining medially without any trace of a median plate ( Figs. 1 , 2 ) (with a small plate present between the pseudorostral spines in Tiaramedon ; cf. Chia & Ng 1998 : fig. 8A, B); the chela is unarmed ( Figs. 1 , 2 , 3 F) (with an additional spine on the dorsal distal margin in Tiaramedon ; cf. Chia & Ng 1998 : figs. 7A, B, 8K); the cheliped carpus has a single long inner spine ( Figs. 1 , 2 , 3 F) (2 large spines in Tiaramedon ; cf. Chia & Ng 1998 : fig. 7A); the ambulatory merus is long and slender with a short dorsal distal tooth ( Figs. 1 , 2 , 4 E) (short and stout with a long distal dorsal tooth in Tiaramedon ; cf. Chia & Ng 1998 : figs. 7, 8C); and the male anterior thoracic sternum is transversely narrow ( Figs. 3 C, 4B) (transversely broad in Tiaramedon ; cf. Chia & Ng 1998 : figs. 7B, 8D). The male abdomens of Cebudonus n. gen. and Tiaramedon are nevertheless similar in shape ( Figs. 3 D, 4C; cf. Chia & Ng 1998 : figs. 7B, 8F). The two genera are also different in terms of host specificity, with Tiaramedon always associated with crinoids (and with young crabs characteristically transversely striped like many other crinoid-associated eumedonines, see Castro et al. 1995 ; Chia & Ng 1995, 1998) whereas Cebudonus n. gen. with its longitudinal stripes is probably associated with echinoids. Cebudonus n. gen. can be separated from the echinoid symbiont Zebrida by having two subcylindrical pseudorostral spines ( Figs. 1 , 2 ) (distinctly lamelliform in Zebrida ; cf. Ng & Chia 2000 : figs. 2, 3A, B); the lateral carapace tooth and the dorsal surface adjacent to the tooth is dorsally convex ( Fig. 3 B) (the area is distinctly dorsally flattened in Zebrida ; cf. Chia et al. 1995: fig. 3B); the chela and merus are unarmed and the carpus has a long spine at the inner angle ( Figs. 1 , 2 , 3 F) (the chela has a large subdistal dorsal tooth, the carpus and merus each having three large lamelliform teeth in Zebrida ; cf. Ng & Chia 2000 : figs. 2, 3J); the ambulatory merus is long and slender with a short dorsal distal tooth ( Figs. 1 , 2 , 4 E) (short and stout with the margins cristate to dentate and with a large distal dorsal tooth in Zebrida ; cf. Ng & Chia 2000 : figs. 2, 3C, K, M); the ambulatory propodus and dactylus are normal ( Figs. 1 , 2 , 4 D, E) (forming a subchelate clasping structure in Zebrida ; cf. Ng & Chia 2000 : figs. 2, 3C, K, M); and the male anterior thoracic sternum is proportionately narrower transversely ( Figs. 3 C, 4B) (proportionately wider in Zebrida ; cf. Ng & Chia 2000 : figs. 2B, 3D). The male abdomens of Cebudonus n. gen. and Zebrida are similar, with both relatively wide transversely ( Figs. 3 D, 4C; cf. Ng & Chia 2000 : figs. 2B, 3F) There are also similarities with Zebridonus but Cebudonus n. gen. can be separated by its two long pseudorostral spines ( Figs. 1 , 2 ) (with a distinctly dorsoventrally flattened lobiform pseudorostrum that is bifurcated distally to form two teeth in Eumedonus ; cf. Chia et al. 1995: figs. 1, 2A, K); the lateral carapace tooth and the dorsal surface adjacent to it is dorsally convex ( Fig. 3 B) (the area is distinctly dorsally flattened in Zebridonus ; cf. Chia et al. 1995: figs. 1, 2A, 3C); the chela and merus are unarmed, and the carpus has a long spine on the inner angle ( Figs. 1 , 2 , 3 F) (the chela has a distinct distal dorsal tooth, the carpus 2 large lamelliform teeth and the merus several distinct teeth in Zebridonus ; cf. Chia et al. 1995: figs. 1, 2 I); the ambulatory merus is long, subcylindrical and smooth, without any marginal cristae and the dorsal distal tooth is relatively low ( Figs. 1 , 2 , 4 E) (short, laterally flattened with distinct marginal cristae and a strong dorsal distal tooth in Zebridonus ; cf. Chia et al. 1995: figs. 1, 2B, C); the anterior male thoracic sternum (sternites 1–4) are proportionately narrower transversely ( Figs. 3 C, 4B) (proportionately wider transversely in Zebridonus ; cf. Chia et al. 1995: fig. 2D); and the male abdomen is proportionately wider ( Figs. 3 D, 4C) (proportionately narrower in Zebridonus ; cf. Chia et al. 1995: fig. 2F).