Amastigia zigzag, Figuerola & Gordon & Cristobo, 2018

Figuerola, Blanca, Gordon, Dennis P. & Cristobo, Javier, 2018, New deep Cheilostomata (Bryozoa) species from the Southwestern Atlantic: shedding light in the dark, Zootaxa 4375 (2), pp. 211-249 : 213

Amastigia zigzag n. sp.

( FIg. 1 ; TAbLE 2)

Etymology. ALLUDINg TO THE ZIgZAg ARRANgEMENT OF THE bASAL AVICULARIA; USED AS A NOUN IN APPOSITION.

Material examined. HΟlΟtype: CRBA-58227, STN PAT 1208DR17. COLONY, AbOUT 40 MM IN HEIgHT, bRANCHES AbOUT 0.7 MM WIDE; WITH PROXIMAL AND DISTAL PORTIONS, SOME bRANCHES bROKEN.

Description. COLONY ERECT, UNILAMINAR, bRANCHINg, COMPRISINg THREE LONgITUDINAL SERIES OF AUTOZOOIDS; COLONY HEIgHT AbOUT 40 MM, AND bRANCH WIDTH AbOUT 0.7 MM. AUTOZOOIDS IN ALTERNATINg LONgITUDINAL SERIES, MORE OR LESS RECTANgULAR; AN OVAL OPESIA OCCUPYINg MOST OF FRONTAL AREA, COMPLETELY CONCEALED bY PROMINENT SCUTUM WITH SEMIELLIPTICAL PROXIMAL LObE, AND TRUNCATED DISTAL LObE THAT IS SOMEWHAT INCLINED FRONTALWARDS; ATTACHMENT POINT OF SCUTUM MEDIAN OR NEAR-MEDIAN. ZOOIDS WITH TWO SPINES AT OUTER DISTAL ANgLE, ONE ON THE INNER CORNER. TWO FRONTAL AVICULARIA, SMALL, THE ROSTRUM PERPENDICULAR TO FRONTAL PLANE, HOOKED, WITH bROADLY TRIANgULAR MANDIbLE. AbFRONTAL SIDE OF bRANCH WITH MEDIAN ZOOIDAL SERIES EXCLUDED; bASAL AVICULARIA PRESENT, ONE PER ZOOID, ANgLED ObLIqUELY PROXIMALLY TOWARDS THE NEXT PROXIMAL AVICULARIUM, FORMINg A SOMEWHAT ZIgZAg SERIES; ROSTRUM AND MANDIbLE ELONgATE-TRIANgULAR. OOECIUM LONgER THAN WIDE, ECTOOECIUM MOSTLY MEMbRANOUS, ITS CALCIFIED MARgIN FORMINg A DISTINCT RIM AROUND THE EXTENSIVE SMOOTHLY CALCIFIED ENDOOECIUM; PAIRED AVICULARIA OCCURRINg AT THE DISTAL END OF THE OVICELL, THE TRIANgULAR ROSTRUM POINTED ObLIqUELY OUTWARD. RHIZOIDS ARISE FROM DISTObASAL WALL OF MARgINAL AUTOZOOIDS.

n, number of measurements made; SD, standard deviation

Remarks. AMONg SOUTH ATLANTIC, SUbANTARCTIC AND ANTARCTIC SPECIES OF Amastigia , SEVEN SPECIES HAVE ZOOIDS WITH LARgE SCUTA: A. abyssicΟla (KLUgE, 1914), A. benemunita (BUSK, 1884), A. crassimarginata (BUSK, 1884), A. funiculata (MACGILLIVRAY, 1886), A. gaussi (KLUgE, 1914), A. magna GORDON, 1986 AND A. puysegurensis GORDON, 1986. A. zigzag n. sp. RESEMbLES A. abyssicΟla AND A. gaussi , bOTH FROM ANTARCTICA, bUT DIFFERS IN THE AbSENCE OF DISTOLATERAL AVICULARIA, A MUCH LARgER EXPOSURE OF THE ENDOOECIUM, AND A LARgER SCUTUM THAT IS ATTACHED TO THE ZOOIDAL MARgIN AT OR NEAR ITS MIDPOINT, NOT DISTALLY. FURTHER, THE bASAL AVICULARIA OF A. zigzag n. sp. DIFFER FROM OTHER SPECIES IN ALTERNATINg IN A ZIgZAg MANNER DOWN THE bRANCH AND IN HAVINg MORE-ELONgATE TRIANgULAR ROSTRA AND MANDIbLES THAN A. gaussi . IN PARTICULAR, A. benemunita IS CHARACTERIZED bY THE PRESENCE OF bASAL AVICULARIA ON SOME MARgINAL AUTOZOOIDS AND, IN THE CASE OF A. funiculata , bASAL AVICULARIA ARE FOUND IN bIFURCATIONS. A. crassimarginata , A. magna AND A. puysegurensis HAVE bASAL VIbRACULA.

Figures

FIGURE1. Amastigia zigzag n. sp., HOLOTYPE.A, PORTION OF A bRANCH;B, DETAIL OF AUTOZOOIDS SHOWINGTHE DISPOSITION OF SPINES AND FRONTAL AVICULARIA; C, OVICELLATE ZOOID SHOWING SOMEWHAT PARALLEL-SIDED OOECIUM WITH DETAIL OF THE OVICELL; NOTE THE THIN ECTOOECIUM CONFINED TO THE MARGIN, AND THE bROAD EXPOSURE OF THE ENDOOECIUM; D, bASAL PORTION WITH AVICULARIA AND RHIZOIDS ARISING FROM DISTObASAL WALL OF MARGINAL AUTOZOOIDS; NOTE THE SOMEWHAT ZIGZAG ARRANGEMENT DOWN THE bRANCH.SCALE bARS: 500 ΜM.