Compactozetidae Luxton, 1988

Colloff, Matthew J., 2023, The oribatid mite superfamily Eutegaeoidea (Acari, Oribatida), with descriptions of new taxa from Australia and New Caledonia and a re-assessment of genera and families, Zootaxa 5365 (1), pp. 1-93 : 54-55

Compactozetidae Luxton, 1988

Compactozetidae Luxton, 1988a, p. 86 .

Type genus: Compactozetes Hammer, 1966, p. 76 .

Diagnosis. The following diagnosis is modified from that of Luxton (1988a). Lamellae well developed, fused with each other apically ( Compactozetes ) or with short, broad, rounded or truncated free cusps ( Sadocepheus and Hamotegeus ). Anterior projections of humeral processes short and blunt; humeral processes originating on lateral margin at widest part of notogaster; posterior region of humeral process with two to four distinct lobes evident from lighter areas of cuticle and wavy lateral margin. Bothridia fused with bases of lamellae, not free. Notogaster circular, broader than long, with nine or ten pairs of marginal setae originating on alveoli or tubercles. Chelicerae chelate-dentate, of normal proportions. Pedotectum I with large curved point or spine, discidium lobe-like, not triangular. Anterior margin of pedotectum I and epimere I forming straight or curved transverse tectum covering posterior mentum. With six pairs of genital setae, three pairs of adanal setae. Circumpedal carina present. Perigenital carinae and enantiophyses E4 present or absent. Anal plates rectangular. Pre-anal organ oval or circular, occasionally with cylindrical apex.

Remarks. Luxton (1988b) included the genera Bornebuschia , Compactozetes , Dicrotegaeus , Hamotegeus and Sadocepheus in his definition of Compactozetidae . Norton and Behan-Pelletier (2009) made Compactozetidae a junior synonym of Cepheidae because of what they considered a lack of family-level diagnostic characters. The genera included in Compactozetidae by Luxton (1988b) initially appear to be morphologically diverse, with an inconsistent, mosaic-like, distribution of shared characters, attributable largely to the inclusion of Bornebuschia and Dicrotegaeus . For example, in Bornebuschia and Dicrotegaeus the notogastral setae are arranged in three ranks (centrodorsal, sub-marginal and marginal; cf. Fig. 13a for distribution pattern), whereas in the other genera the setae are all marginal. Dicrotegaeus has extremely long, pointed lamellae that extend well beyond the rostrum, unlike those of Compactozetes , Bornebuschia and Hamotegeus which generally do not extend beyond the rostrum, have blunt, transverse or oblique free cusps or the cusps are fused with each other and the rostrum (in Compactozetes ). Bornebuschia , Dicrotegaeus and some Compactozetes spp. have perigenital carinae and enantiophyses E4 (as does Porrhotegaeus herminae J. and P. Balogh, 1983c in the Porrhotegaeidae fam. nov., Humerotegaeus and Neoeutegaeus spp. in the Neoeutegaeidae and most species of Pterozetidae ), whereas the compactozetid genera Hamotegeus and Sadocepheus lack these structures. Bornebuschia and Dicrotegaeus have well-developed enantiophyses H on the posterior prodorsum and anterior notogaster, as well as anterior condyles of enantiophyses B, not found in other Compactozetidae but present in some species of Neoeutegaeus and Sadocepheus spp. Bornebuschia and Dicrotegaeus also have only two pairs of adanal setae, whereas all Compactozetidae have three pairs, though most species of Neoeutegaeus have two pairs ( N. phyllophorus has three pairs; cf. above). Hamotegeus , Sadocepheus spp. and Compactozetes have elongated humeral processes, extending from a point level with notogastral setae lm and with two to four lobes of lighter cuticle separated by indentations and a square or trapezoid anterior lobe with a pointed or rounded apex. This latter character state is a family-level synapomorphy within the Eutegaeoidea , as is the rectangular (rather than lozenge-shaped) anal plates. Finally, Compactozetes zeugus Luxton 1988b , Sadocepheus foveolatus Luxton, 1988b and Hamotegeus spp. have the marginal notogastral setae (l and h series) emerging from tubercles rather than alveoli and Sadocepheus elevatus Mahunka, 1987 has seta la only on a tubercle, the others emerging from alveoli. Notogastral setae emerging from tubercles is a synapomorphic generic character state within the Eutegaeoidea , though clearly not all Compactozetidae share this state.

J. Balogh and Mahunka (1969, p. 2) defined Hamotegeus has having ten pairs of notogastral setae, of which seven pairs are on tubercles (‘basally incrassate’) on the notogastral margin, and with six pairs of genital setae, with humeral processes and cylindrical bothridia projecting anteriorly and laterally (‘pro- and exclinate’). They stated (p. 4) that Hamotegeus “…takes an intermediate position between the genus Cepheus , Compactozetes and Eutegaeus . Owing to the combination of characters given above, the new genus cannot be relegated to either one.” Subías (2004, p. 84) made Hamotegeus the junior synonym of Sadocepheus , though without giving reasons. Ermilov (2020a, p. 877) agreed, stating of Hamotegeus : “It is very similar to Sadocepheus distinguishing [sic] from the latter by such important traits as, e.g. the location of dorsal notogastral setae on tubular tubercles and the position of notogastral setae h 1 very close to each other. However, these traits were not unique. For example, Sadocepheus foveolatus Luxton, 1988 also has dorsal notogastral setae inserted on tubular tubercles; Sadocepheus makarchevae Sitnikova, 1975 and Sadocepheus elevatus Mahunka, 1987 also have notogastral setae h 1 inserted close to each other.”

Luxton (1988a) differentiated Hamotegeus from Sadocepheus on the basis that Hamotegeus has ten pairs of notogastral setae on apophyses or tubercles, whereas Sadocepheus has nine pairs on alveoli. However, as noted above, S. foveolatus Luxton, 1988b has the l and h series on tubercles. P. Balogh (1986) noted that in H. longiseta and H. breviseta seta la is positioned in a ventro-lateral position between the humeral process and the bothridum, but la is absent in H. franzi and H. granulatus J. Balogh & Mahunka, 1969 . Thus Hamotegeus has either nine or ten pairs of notogastral setae. Regarding the positioning of setae h 1, in H. breviseta , H. franzi and H. granulatus both setae emerge from a single tubercle, whereas in H. longiseta there are two tubercles that are adjacent but not connected.

Other than the arrangement of the notogastral setae, there are additional character states that differentiate Hamotegeus from Sadocepheus . Like Sadocepheus and Compactozetes , the humeral processes in Hamotegeus originate on the margin of the notogaster at its widest part but their apices are short and strongly bilobed, projecting obliquely from the anterior margin of the notogaster, whereas in Sadocepheus they are similar to those of Compactozetes : elongated, with several lateral lobes and a square or trapezoid anterior lobe with a broad, pointed apex. In Hamotegeus the dorsosejugal scissure is convex, whereas in Sadocepheus it is transverse. In Hamotegeus pedotectum I is short with a pointed apex and pedotectum II consists of a short, curved lobe, whereas in Sadocepheus pedotectum I is prominent, often considerably expanded laterally and with a large, curved, horn-like apex and pedotectum II is large, laterally projecting and either square or trapezoid or with long, diagonally-sloping anterior margins. In Hamotegeus the genital setae are extremely long, much longer than the width of each genital plate, representing an autapomorphy within the Eutegaeoidea (and H. breviseta exhibits genital neotrichy, with 7-9 pairs of setae), whereas in Sadocepheus the genital setae are shorter than the width of each genital plate. For these reasons I reject the proposition of Subías (2004) that Hamotegeus is a junior synonym of Sadocepheus .

In the generic composition of the Compactozetidae , I retain Compactozetes , Sadocepheus and Hamotegeus but establish a new family, Bornebuschiidae fam. nov. (cf. below) for Bornebuschia and Dicrotegaeus . Differences between Compactozetidae and Pterozetidae are detailed under the remarks section for the latter family below.

Figures

FIGURE 13.Atalotegaeus crobylus sp. nov., adult (a) dorsal aspect showing notogastral setae in the centrodorsal position (cd), sub-marginal (sm) and marginal (m) positions; (b) ventral aspect. Scale bar = 200 μm.