Deckenia imitatrix Hilgendorf, 1869a: 2 Ortmann, 1902: 306 Bott, 1955: 219 Ng et al ., 1995: 583 Cumberlidge, 1997: 574 1998: 194–195 Brachyura: Potamoidea: Potamonautidae, Platythelphusidae, Deckeniidae () Reed, Sadie K. Cumberlidge, Neil Zootaxa 2006 2006-07-17 1262 1 1 139 Hilgendorf, 1869 Hilgendorf 1869 [308,750,283,310] Malacostraca Potamonautidae Deckenia Animalia Decapoda 41 Arthropoda species imitatrix      Deckenia imitatrix Hilgendorf, 1869a: 2;  Ortmann, 1902: 306;  Bott, 1955: 219, fig. 6, pl. 1 fig. 1a– d; Pretzmann, 1977: figs 17–20;  Ng et al., 1995: 583, tables 1,2;  Cumberlidge, 1997: 574;  1998: 194–195.   Type material examined: TANZANIA: Zanzibar, female cw 35.4, cl 29.2 mm( lectotype, designated by Bott 1955: 220) (von der Decken) ( ZMB3216). There is reason to believe that the type locality is actually in Kadiaro, Kenya ( Marijnissen et al. 2005).  Additional material examined:   TANZANIA: South Pare Mountains, Bumba, near Gonja, from rice fields,  29.v.1968( J. N. Raybould) ( NMU TRW1968.04).   KENYA: Malindi, male,  vi.1934( A. Loveridge) ( USNM 70915);  Mombasa, from temporary rainwater pool in the center of town, male,  vii.1903( Ch. Alluaud) ( USNM 32298);  Mombasa, ( Joy) ( NMU23.02.1972.1);  Simakeni Dam, west of Rabai, 15 kmnorthwest of Mombasa, rainfed water body, no inlet or outlet, about  30 mwide,  1.7 mdeep, highly turbid, crabs caught by sweep netfrom depths of 30 cmor more, some crabs seen swimming,  16.vii.1980(A. W. R. McCrae) ( NMU 1980.03);  Mombasa, ( Joy) ( NMU 07.2001.e.1);  Coast Province, Kilifi District, Arabuko­Sokoke Forest, 1998 ( J. Ashe via R. C. Drewes) ( NMU 1998).   SOMALIA: Giohar, adult male,  vii.1968( Lanza) ( NHMW 4369).   Diagnosis.Exorbital tooth pointed; infraorbital margin lined with long sharp spines; epibranchial tooth sharp spine; ischium of cheliped with sharp spine; inferior margins of merus of cheliped lined with sharp spines; upper margin of merus of cheliped with row of pointed teeth, distal tooth longest; anterior inferior margin of merus of cheliped with large distal tooth; outer margin of carpus of cheliped with two sharp spines; first, second carpal teeth on inner margin of carpus of cheliped subsequal sharp spines; inner/outer margins of carpus of p2 lined with sharp subdistal spines; dorsal margin of merus of p2–p5 with sharp subdistal spine; interior margin of propodus of p2–p5 with row of sharp spines; terminal article of gonopod 1 clearly separated from subterminal segment by distinct line; proximal region of terminal article slim, subconical, tapering to cylindrical distal part. Chelipeds of adult males equal­sized, not markedly heterochelous.   Distribution.East African coastal region, from northeast Tanzaniato Taru, Kenya, to Giohar and Eil, Somaliaand inland in Kenyaas far as Nairobi. Marijnissen et al. (2005)argued that the typelocality is Kadiaro, Kenya(and not Zanzibar), and that the report of  D. imitatrixfrom Zanzibaris most probably the result of a mistake arising from the replacement of a lost label.   Remarks. Bott (1955)and Pretzmann (1977)included photographs of this East African species, while Ng et al. (1995)provided illustrations of the gonopods, the mandibles and the unusual mouthparts.  Deckenia imitatrixis distinguished from  D. mitisby the teeth on the infraorbital margin (which are sharp spines in  D. imitatrixand low, broad and blunttipped in  D. mitis) and by the inner and outer margins of the carpus of the cheliped (which possess sharp spines in  D. imitatrixand low broad, blunt­tipped teeth in  D. mitis).  Natural history and conservation status.The conservation status of  D. imitatrixis currently categorized as least concern (LC) ( Table 4) because it has a range of occurrence and area of occupancy well in excess of the thresholds for vulnerable (VU) ( IUCN 2004). Its population levels were estimated to be stable based on indirect measures such as the fact that it has been collected recently from more than one locality and that it is well represented in museum collections. However, recent field surveys by S. Marijnissen (pers comm.) have revealed that this species may be potentially more vulnerable that previously thought. Although this species has a wide extent of occurrence that is much greater than 20,000 sq. km. (which is above the threshold for vulnerable, VU), it may have an increasingly restricted area of occupancy due to habitat disturbance that would fall into the range for vulnerable (VU). While it is difficult to estimate the population status and trends of this species, its population is estimated to possibly in decline due to the fact that its habitat is restricted to marshes and wetlands, and these are fragmented and declining in this part of East Africa ( IUCN 2004; Table 4). The dependence of this species on wetland habitats that are vulnerable to human disturbance and that are associated with a growing human population in the region would argue for the upgrading of the conservation status of  D. imitatrixfrom least concern to vulnerable in the light of the new data. 1968-05-29 NMU J. N. Raybould Tanzania South Pare Mountains Gonja Bumba 41 TRW1968.04 1 1934-06 USNM A. Loveridge Kenya Malindi 41 USNM 70915 1 1903-07 USNM Ch. Alluaud Kenya Mombasa 41 USNM 32298 1 Mombasa NMU Kenya Joy 41 1 Mombasa 1980-07-16 R McCrae Kenya 30 Rabai Simakeni Dam 41 NMU 1980.03 1 Mombasa [673,1117,871,897] NMU Kenya Joy 41 NMU 07.2001 1 Mombasa R J. Ashe & C. Drewes Kenya Arabuko-Sokoke Forest Coast Province 41 NMU 1998 1 Kilifi [264,1038,950,977] 1968-07 NHMW Lanza Somalia Giohar 41 NHMW 4369 1