Crotonia ramus ( Womersley, 1957 )

Colloff, Matthew J. & Perdomo, Giselle, 2009, New species of Crotonia (Acari: Oribatida: Camisiidae) from Nothofagus and Eucalyptus forests in Victoria, Australia, with a redescription of the fossil species Crotonia ramus (Womersley, 1957), Zootaxa 2217, pp. 1-36 : 27-30

† Crotonia ramus ( Womersley, 1957)

( Figs. 16 , 19 )

Acronothrus ramus Womersley, 1957 , p. 22, Fig. 11 .

Crotonia ramus ( Womersley, 1957) : Wallwork, 1977, p. 525.

Dimensions. Holotype: a damaged female with several dorsal setae broken off; length 705 breadth 362; ratio of length of prodorsum to total length: 0.4.

Female. Prodorsum: rostrum rounded, not prominent; rostral setae (ro) short, spiniform, 15 ( Fig. 16 a). Lamellar setae (le) 130, recurved, barbed. Lamellar apophyses 58, half as long as their mutual distance; extending anteriorly as far as bases of rostral setae. Interlamellar apophyses twice as long as broad; interlamellar setae (in) broken off. Prodorsal ridges extending two thirds of the distance between interlamellar and lamellar apophyses. With inter-bothridial ridge in the form of a shallow curve; cuticle posterior of ridge smooth. Median field of muscle sigilla present. Prodorsum porose.

Notogaster: ratio of length to breadth 1.54; broadest between cp and e 2 ( Fig. 16 a). Dorsosejugal suture discrete, simple. With 13 pairs of notogastral setae; c 3, f 1 and h 1 broken off. Pre-notogastral shield bearing relatively long, 72, setiform setae c 1 and separated from notogastral shield by transverse hyaline strip. Apophyses of setae c 3 very well-developed, 32, twice as long as broad. Notogastral shield discrete, porose; bordered laterally by two narrow strips lacking pori, extending posteriorly almost as far as setae f 2. Region posterior of setae f 2 with sparse tubercles. Lateral hyaline strip (suprapleural scissure) bearing alveoli of setae cp, and e 2. Tubercles of setae f 2 squat, projecting beyond lateral margin. Setae f 2 spiniform, barbed, short, 23. Setae cp and e 2 and subequal, 58; setae d 2 slightly shorter, 47, but well-developed, setiform. Opisthosomal gland opening gla positioned ca. 35 anterior of f 2. Apophyses of setae f 1 emerging from dorsal surface of apophyses of setae h 2, projecting posteriolaterally, adjacent and parallel with those of h 1, and subequal, 20, to them. Setae f 1, h 1 and h 3 broken off holotype specimen. Setae h 2 short, 30, spinose, barbed; their apophyses relatively long, 65, parallel for most of their length, slightly diverging apically; caudal margin between them an inverted U-shape.

Ven t er: epimeres porose ( Fig. 16 b); epimeral setae smooth, spiniform, formula 3-2-3-3; setae 3c on welldeveloped tubercles. Genital plates sub-circular. Each plate 95 long, 56 broad with eight spiniform setae. Anal plate 30 broad, 165 long, with three pairs of stout setiform setae, 22; Ventral margin of notogaster surrounding anal plates U-shaped. Setae p 2 and p 3 curved, subequal, 24, p 1 60, recurved, stout, barbed, on well-developed tubercles, 15 very close together.

Material Examined and Locality Data. Holotype female from block of fossilized resin (retinite) of late Tertiary age, probably Pliocene, near Ballarat in the Victorian goldfields. This species was in the Department of Geology, University of Melbourne, transferred to Department of Invertebrate Palaeontology, Museum Victoria from whence it was loaned. Permission was given to the first author to remount the holotype because the notogaster was obscured by debris. Unfortunately, the specimen was lost during the process.

Remarks. Womersley (1957) illustrated this species with the caudal tritonymphal exuvium intact. This was removed during remounting and cleaning by the first author to reveal short spiniform adult setae f 2 and h 2 rather than the long, curved tritonymphal setae illustrated in Womersley’s Figure 1 , as well as the more elongated nature of the caudal region and apophyses. Setae c 3 appear to have been broken off the holotype specimen prior to the original description, but the presence of massive protuberant apophyses strongly suggest that setae c 3 were elongated, flagelliform and probably longer than c 1.

Crotonia ramus differs from other members of the genus by the following combination of characters: 1) it is by far the smallest member of the genus - the next longest (812) being C. chiloensis Wallwork, 1977 ; 2) setae d 2 are long, well-developed, almost as long as cp and e 2; 3) setae f 2 are spiniform, barbed; 4) the notogastral shield is porose, with two narrow lateral strips lacking tubercles; 5) setae p 1 are stout, reflexed, barbed and positioned adjacent to each other; 6) with the epimeral setal formula 3-2-3-3. It is morphologically most similar to C. momitoi sp. nov. from which it differs by its smaller size, in the shape of the apophyses of setae h 2, the morphology of setae f 2 and p 1, the absence of narrow lateral strips of small tubercles on the notogastral shield, a less prominent rostrum and rostral setae and the presence of barbed ornamentation on the lamellar setae.

Figures

FIGURE 1. Crotonia alpina sp. nov. holotype female a) dorsal; b) ventral.

FIGURE 11. Crotonia blacki sp. nov. protonymph a) dorsal; b) ventral

FIGURE 16. Crotonia ramus (Womersley, 1957). Holotype female a) dorsal; b) ventral.

FIGURE 19. Distribution map of Crotonia spp. in Victoria. Stippled area is the distribution of the broad vegetation group categorised as ‘ wet or damp forests’ (Department of Sustainability and Environment, 2005). NP = National Park; SF = State Forest. Black circles are towns and cities, provided for spatial reference. Inset: 30 - year means of annual rainfall (source: Australian Bureau of Meteorology, www. bom. gov. au).