PACHYLASMATIDAE UTINOMI, 1968 EMEND

Chan, Benny Kwok Kan, Corbari, Laure, Rodriguez Moreno, Paula A. & Tsang, Ling Ming, 2017, Molecular phylogeny of the lower acorn barnacle families (Bathylasmatidae, Chionelasmatidae, Pachylasmatidae and Waikalasmatidae) (Cirripedia: Balanomorpha) with evidence for revisions in family classification, Zoological Journal of the Linnean Society 180 (3), pp. 542-555 : 552-553

FAMILY PACHYLASMATIDAE UTINOMI, 1968 EMEND

Pachylasmatinae Utinomi, 1968: 37

Pachylasmatidae Foster, 1978: 76 . – Buckeridge, 1983: 61. – Jones, 2000

Diagnosis: Shell wall comprises eight distinct calcareous plates (R-RL-CL1-CL2-C) with compound rostrum. Plates 8, 6 and 4 differentiated externally in adults. Caudal appendage present, cirrus III resembles cirrus II and not cirrus IV. Radii absent, and suture edges not complexly interlocked. Imbricating plates absent.

Remarks: Pachylasma was first identified by Darwin (1854), and these barnacles are considered exclusively deep-sea species. When Darwin examined the morphology of Pachylasma , he discovered that the Pachylasma shell is balanid-like; however, the somatic body is a feature of chthamalid species ( Darwin, 1854). Darwin (1854) classified Pachylasma in Chthamalidae and concluded that Pachylasma was likely the point of contact in the chthamalid and balanid barnacle evolution ( Darwin, 1854). The Jones (2000) classification includes five subfamilies in Pachylasmatidae , namely Eolasmatinae Jones, 2000, Pachylasmatinae , Metalasmatinae Jones, 2000, Bathylasmatinae and Hexelasmatinae. Our study indicated that Bathylasmatinae and Hexelasmatinae belonged to Tetraclitoidea , supporting the proposal by Newman & Ross (1976) and Buckeridge & Newman (2010). Therefore, Pachylasmatidae currently comprises three subfamilies, Eolasmatinae, Pachylasmatinae and Metalasmatinae. The genera and species proposed in Metalasmatinae are based on the classification of Jones (2000). According to Jones (2000), Eolasmatinae comprises the fossil genera Eolasma , in which the specimen was described on the basis of a limited number of disarticulated plates, and Waikalasma . Ross & Newman (2001) erected a new family Waikalasmatidae in Chionelasmatoidea to accommodate Waikalasma because Eolasma lacks imbricating plates around the shells, unlike Waikalasma . In the present study, Waikalasma formed a distinct molecular clade with other familial groups, supporting the proposal of familial ranking for Waikalasmatidae Ross & Newman (2001) .

In the present study, Pseudoctomeris was located in the same molecular clade as Pachylasma . The genera in the subfamily Pachylasmatinae was revised as follows:

SUBFAMILY PACHYLASMATINAE UTINOMI, 1968 EMEND

Pachylasmatinae Utinomi, 1968: 37 . – Newman & Ross, 1976: 36. – Jones, 2000: 163.

Diagnosis (Emend): Shell without imbricating plates and covered externally with eight, six, or four solid plates. Parietes without chitin. Opercular plates partially fused or separated. Membranous base. The subfamily includes intertidal and deep-sea species.

Remarks: The type genus is Pachylasma . Our study follows the classification of Jones (2000) that Pachylasmatinae contains Eutomolasma , Microlasma Jones, 2000 , Pachylasma , Eurylasma and Tetrapachylasma , with the addition of Pseudoctomeris . Pseudoctomeris sulcata ( Nilsson-Cantell, 1932) was grouped with Pachylasma in the present molecular phylogeny. Pseudoctomeris sulcata was first classified in the Chthamalidae (see Nilsson-Cantell, 1932) based on its solid shells and with a membranous base. However, Hiro (1939) reexamined Pseudoctomeris in detail and revealed that P. sulcata shared morphological similarities with Octomeris Sowerby, 1825 and Pachylasma . Pseudoctomeris sulcata was morphologically close to Pachylamsa because it has Pachylasma - type opercular plates and a compound rostrum, in which the rostrum was joined with rostral laterals by a straight suture. Furthermore, P. sulcata has caudal appendages, whereas Octomeris lacked caudal appendages ( Hiro, 1939). Hiro (1939) proposed that P. sulcata should be identified as Pachylasma . However, he believed that Pachylasma is an exclusive deep-sea taxon, whereas Pseudoctomeris is an intertidal inhabitant. He later recognized P. sulcata as a member of Octomeris . Poltarukha (1996), based on the distinct differences between P. sulcata and Octomeris , erected a new genus Pseudoctomeris to accommodate P. sulcata , under the subfamily Euraphinae in Chthamalidae . In the present study, molecular phylogenetic analysis showed P. sulcata was grouped in the clade of Pachylasmatidae . This result is also supported by the molecular analysis in Pérez-Losada et al. (2014) in which P. sulcata was positioned in the Pachylasmatoidea clade. On the basis of Pseudoctomeris possessing Pachylasma - type opercular plates, a compound rostrum and with the presences of caudal appendage, the present study grouped Pseudoctomeris in Pachylasmatidae . The genus Pseudoctomeris is monotypic, containing P. sulcata and this species represents the only intertidal species in Pachylasmatidae and has eightplated shells (compound rostrum).

TAXONOMIC REVISION OF TETRACLITOIDEA S. L. ( BATHYLASMATIDAE )

SUPERFAMILY TETRACLITOIDEA GRUVEL, 1903

Tetraclitidae Gruvel, 1903: 160 .— Newman & Ross, 1976: 37

Tetraclitoidea Newman, 1993: 408 .

Diagnosis: Six- or four-walled plates, solid parietes, permeated with chitin-filled tubes, with one or more rows of tubes containing living tissue or filled with calcareous materials. Plates with or without radii. Caudal appendages absent (diagnosis follows Newman & Ross, 1976).

Remarks: In the Tetraclitoidea superfamily, three families are proposed: Austrobalanidae , Bathylasmatidae and Tetraclitidae .

BATHYLASMATIDAE NEWMAN & ROSS, 1971

Bathylasmatidae Newman & Ross, 1971: 138 . – Newman & Ross, 1976: 37; Buckeridge & Newman, 2010: 40; Table 1.

Diagnosis: Four- or six-plate shells, solid-plate shells or permeated with a single row of chitin-filled tubes. Radii absent. An inferior margin of mandible bearing a few small spines. All cirri without specialized setae. One or both rami of cirrus III, or sometimes cirrus II, may be antenniform.

Remarks: Hoek (1913) erected the genus Hexelasma in Balanidae to accommodate the deep-sea species discovered in the Challenger and Siboga expeditions, where the shells of these barnacles were balanid-like; however, the labrum lacked a notch, and cirrus III resembled cirrus IV instead of cirrus II. The morphology of such labrum and cirrus III of Hexelasma differed from those of the balanid barnacles. Pilsbry (1916), based on the morphology of the labrum and cirrus III, relocated Hexelasma from Balanidae to Chthamalidae . Bage (1938) argued that this position was the appropriate Hexelasma taxonomic position because this genus had features of both balanid and chthmalid barnacles. In Newman & Ross (1976), Bathylasmatidae was composed of two subfamilies: Bathylasmatinae and Hexelasmatinae. In the present study, we have samples only from Hexelasma and Bathylasma for molecular phylogenetic analysis. The taxonomic status of these two subfamilies should be evaluated following a phylogenetic reconstruction covering all five genera, including Bathylasma , Mesolasma , Tessarelasma , Tetrachaelasma ( Jones, 2000) and Hexelasma (type genus). At present, we follow the classification of Newman & Ross (1976) that Bathylasmatidae is composed of Bathylamatinae and Hexelasmatinae.