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Systematic palaeontology
Remarks – Despite our efforts over the past 20 years to expand the recorded fauna of fossil brachiopods from Jamaica, sample sizes of known taxa have commonly remained small. Thus, ontogenetic and size-independent intra-specific variation has been difficult to define and assess. Moreover, irrespective of the small size of samples, little information is available regarding the internal features of the majority of the described species; a number of generic assignments have thus been provisional.
An exception is the terebratulid assemblage of the Manchioneal Formation, now represented by dozens of specimens and described below. Wherever possible, species descriptions are supplemented by measurements and some statistical information; some interspecific comparisons have been effected by Principle Component Analysis (PCA). These PCA analyses have informed our taxonomic methodology concerning those species identified from both Barbados and Jamaica. It is apparent that there are differences, perhaps worthy of nominal subspecific status, between Jamaican and Barbadian samples of two of the three commoner species found in both islands. However, whereas the Manchioneal Formation has over one hundred brachiopods, the Coral Rock, with the exception of the Tichosina shell bed (locality B3), has yielded only tens. The latter are insufficient to permit the rigorous statistical definition of new subspecies. We therefore elect to take a conservative approach, and ‘lump’ the samples from Barbados and Jamaica together, but nevertheless highlight those inter-island differences that are apparent.
The following abbreviations have been used for measurements (in mm): saglv - sagittal length of ventral valve; sagld - sagittal length of dorsal valve; mwi - maximum width; hwi - hinge width; pmwi - position of maximum width; dpv - maximum depth of ventral valve; dpd - maximum depth of dorsal valve.
Order Theceida Elliot, 1958
Superfamily Thecideoidea Gray, 1840
Family Thecideidae Gray, 1840
Subfamily Lacazellinae Backhaus, 1959
Genus Lacazella Munier-Chalmas, 1880
Type species – Thecidea mediterranea Risso, 1826, by original designation; from the Recent of the Mediterranean Sea.
Lacazella sp. cf. L. caribbeanensis Cooper, 1977
next sectionPl. 1, fig. 1
Material – A single specimen in the Lucas Barrett collection, BMNH B 21988 and a further valve in the collections of the Geological Museum, University of Copenhagen, both from Jamaica. A valve from the Middle Coral Rock of Barbados is also reposited in the Geological Museum, University of Copenhagen.
Description and measurements – See Harper (1993).
Discussion – Until further specimens of this taxon become available, little can be added to the comments made by Harper (1993). However, despite its rarity in the fossil record of Jamaica, it is worthwhile re-emphasising that extant L. caribbeanensis Cooper, 1977, is also known from the Tertiary of Cuba and the Dominican Republic (Cooper, 1979; Logan, 1987). Our inability to find more than one further specimen in the Manchioneal Formation, after many years of collecting, has been frustrating, but strongly indicates that this species is rare within this unit. However, it is also conceivable that our interpretation of the horizon from which it was collected may be erroneous, although we do not consider this likely. One valve of this species has also been collected from Barbados.
Occurrence – The label of BMNH B21988 states that this specimen is from the “newer Pliocene” of Jamaica. This is interpreted to be the Manchioneal Formation. However, in over 140 years since Barrett’s original discovery only one further specimen has been collected from Jamaica. As noted by Trechmann (1930, p. 216), “...the Manchioneal beds have been referred by most writers to the Pliocene ...”, a position with which he agreed with “... some doubt ...” and considered that “... Possibly if they were in Europe the Manchioneal [Formation] and perhaps also the Bowden [shell] beds might be placed in the Pliocene rather than the Miocene.” This was at a time when the Bowden shell beds, recognised to be older than the Manchioneal Formation, were considered to be Middle Miocene (Woodring, 1928; Trechmann, 1930, p. 200); they are now identified as Upper Pliocene (Donovan, 1998, and references therein).
Remarks – A printing error in Harper (2002a, table 12.1) omitted the symbol ‘J’ (for Jamaica) in the ‘Pleistocene’ column for this taxon.
Order Terebratulida Waagen, 1883
Suborder Terebratulidina Waagen, 1883
Superfamily Terebratuloidea Gray, 1840
Family Terebratulidae Gray, 1840
Subfamily Tichosininae Cooper, 1983
Genus Tichosina Cooper, 1977
Type species – Terebratula floridensis Cooper, 1977, by original designation; from the Recent of the Caribbean and Gulf of Mexico.
Tichosina inconstanta sp. nov.
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Holotype – A conjoined pair, MGUH 28767 (Pl. 1, fig. 4a, b) from the Manchioneal Formation, Christmas River (J3), Jamaica.
Type locality and horizon – Christmas River, Manchioneal Formation (J3) (lower Pleistocene).
Material – About 400 shells of this species have been collected from localities on both Jamaica and Barbados.
Derivation of name – Name referring to the morphological variation seen in the species.
Diagnosis – Large, ventribiconvex Tichosina species of elongate oval to tear-drop shaped outline, variably uniplicate; pedicle foramen of moderate diameter.
Description – Large ventribiconvex valves, elongate oval to tear-drop shape outline. Maximum width over twice hinge width, occurring at about two-thirds valve length; cardinal extremities obtuse and rounded. Anterior commissure rectimarginate to sulcate; lateral commissures curved. Ventral valve almost nine-tenths as wide as long and about one-third as deep as long. Anterior profile uniformly convex; lateral profile with maximum curvature at umbo, elsewhere surface evenly curved except over anterior third where valve slopes steeply towards anterior commissure. Pedicle foramen variable, circular, oval or labiate, permesothyrid and of moderate diameter. Dorsal valve almost as wide as long and about one-fifth as deep as long. Anterior profile flatly convex with shallow, broad sulcus developing anteriorly from near mid-valve length; lateral profile convex over posterior half of valve, elsewhere surface slopes anteriorly. Ornament of variably accentuated, but subdued, concentric growth lines.
Ventral interior with small, elongate teeth and short pedicle collar. Dorsal interior with narrow loop; outer hinge plates, long and concave; flat-bladed crural bases form raised margin to outer hinge plates. Broad crura with wide transverse ribbon.
Statistics –
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Discussion – The Jamaican material was originally compared (Harper, 1993) with Tichosina? lecta (Guppy, 1866), first described from the Eocene of Trinidad and subsequently re-described from the type area by Cooper (1979). This species is also reported from the Miocene and Pliocene of the Dominican Republic (Logan, 1987), although that material was relatively rare and poorly preserved. Based on data from Cooper (1979) and Logan (1987), a pooled sample of all three forms was investigated by PCA for the following variates: saglv, sagld, mwi and thickness (= dpv+dpd). Differentiation was achieved with respect of scores on the third eigenvector. The type specimens from Trinidad had higher scores (0.20, 0.42) on this eigenvector than the specimens from Jamaica and the Dominican Republic. The direction cosines of the third eigenvector (-0.69, -0.20, 0.60, 0.36) indicate the type T.? lecta to have relatively shorter, wider and more globose shells than those of the other two forms (Harper, 1993). However, larger samples of all three are required to confirm these apparent differences. More recent assessments of the Jamaican material (e.g., Harper et al., 1995) have compared it with T.? bartletti (Dall, 1920), a living species from the Caribbean with a more pronounced uniplicate anterior margin (Cooper, 1977). The large samples now available of the Pleistocene form together with details of its internal features allow, first a confident assignment to Tichosina and second the establishment of a new species. The cardinalia of the new species have the flat-bladed crural bases that are diagnostic for the genus. The large size, elongate oval shape and variably uniplicate anterior commissure associates the Pleistocene material with only T.? bartletti. However, that species has a small pedicle foramen and a more marked plication.
The large samples now available from both Jamaica and Barbados indicate extreme variation in the external morphology of this species. In fact, a large specimen of this species was originally ascribed to Gryphus? (Harper, 1993); information on the interior of that specimen is unfortunately lacking, but it now seems more probable, in view of the large and continuous sample variation now apparent (see statistics above), that the specimen should be included within the new species. It seems unlikely that populations of two or more species have been mixed; rather, the Pleistocene form of T. inconstanta had a fairly plastic external shape. It is also possible that the material described from Miocene and Pliocene of the Dominican Republic (Logan, 1987) may also belong within T. inconstanta, but more material of the latter is required to test this.
Although a large number of specimens of Tichosina are known from Barbados only two have yielded a complete set of measurements. These, together with a sample of 35 specimens from Jamaica, including the conjoined valves previous assigned to Gryphus? sp., were subjected to a PCA interrogation of the correlation matrix based on the following variates: saglv, sagld, mw, hinw, pmw, dpv and dpd. The first two eigenvectors account for 95% of the variation. The Barbados material could not be separated on these or indeed the next two eigenvectors that accounted together for further 2% of the sample variation. With regard to the variates analysed, both samples, including Gryphus? sp., are considered conspecific.
Occurrence – This species is comon on Jamaica at the type section of the Manchioneal Formation (J2) and Christmas River (J3), and occurs at Cruikshank Bay (J1) and Folly Point (J5); approximately 240 shells of this species are now known from the Jamaican localities. Additionally, eight specimens in the Lucas Barrett collection (BMNH) are from the ‘Tertiary and newer Pliocene’ of Jamaica (= Manchioneal Formation; see above). The localities on Barbados, Skeete’s Bay, Whitehaven (B1), Cluff’s Bay (B2) and Spring Bay, Ragged Point (B3) have yielded almost 160 shells; although a large number were recovered from the shell bed at Spring Bay, Ragged Point (B1), most are incomplete.
Superfamily Cancellothyridoidea Thomson, 1926
Family Cancellothyrididae Thomson, 1926
Subfamily Cancellothyridinae Thomson, 1926
Genus Terebratulina d’Orbigny, 1847
Type species – Anomia retusa Linné, 1767, by original designation; from the Recent of Norway.
Terebratulina manchionealensis sp. nov.
Pl. 1, fig. 8; Pl. 3, figs. 3-6.
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Holotype – A disarticulated conjoined pair, MGUH 28774a, b (Pl. 3, figs. 5, 6) from the Manchioneal Formation, Christmas River (J3), Jamaica.
Type locality and horizon – Christmas River, Manchioneal Formation (J3) (lower Pleistocene).
Material – About 90 shells of this species have been collected from localities on both Jamaica and Barbados.
Derivation of name – Named after the Manchioneal Formation on Jamaica from whence the majority of the Pleistocene specimens were collected.
Diagnosis – Small, elongately oval to subtriangular Terebratulina species with ventral sulcus and subcarinate dorsal valve. Usually 6-8 ribs per 2 mm at 5 mm growth stage.
Description – Small, dorsibiconvex valves of elongately oval to subtrigonal outline. Maximum width about twice hinge width, occurring at or near mid-valve length; cardinal extremities obtuse and rounded. Anterior commissure uniplicate. Ventral valve about nine-tenths as wide as long and about one-fifth as deep as long. Anterior profile with narrow, relatively deep median sulcus originating near prominent umbo and developing anteriorly; flanks convex medianly with steep lateral slopes. Lateral profile convex with maximum curvature at mid-valve length. Large suboval pedicle foramen perforates shell apex. Dorsal valve about as long as wide and about one-fourth as deep as long. Anterior profile subcarinate with prominent median fold and sloping, slightly concave flanks; lateral profile uniformly convex with marked umbo. Ornament of variably accentuated costae and costellae numbering 5-8 per 2 mm at 5 mm growth stage on 1, 7, 9 and 8 valves, and arising by both bifurcation and intercalation.
Ventral interior with short pedicle collar; large, elongate teeth. Dorsal interior with small transverse cardinal process; socket ridges thin and elevated. Crural processes directed ventrally and medianly, but distal extensions either broken or obscured; anterior part of loop, concave and flattened.
Statistics –
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Discussion – Initial studies of this species suggested that the distinctive outline, development of the dorsal fold and ventral sulcus together with the style and density of the radial ornament invite a close comparison with T.? palmeri Cooper from the Miocene of Cuba. Cooper (1979, p. 7) considered, however, that T.? palmeri was rather anomalous. Apart from having a subcarinate dorsal fold and narrow ventral sulcus, the species lacked a complete loop; the crural processes are directly dorsally, but only slightly medianly, obviating the possibility to unite and form a loop. This same configuration is not apparent in the few dorsal interiors available from Barbados. Both groups of species are thus no longer considered congeneric. Cooper (1979, p. 7) suggested that the loop was much more similar in orientation and structure to that of Chilidonophora rather than that of Terebratulina. The possibility of homoplasy or the reassignment of the T.? palmeri to the Chilidonophoridae requires further material of Cooper’s species together with a rigorous phylogenetic analysis of the group.
The large sample now available indicates that there are further differences between the Pleistocene form and Cooper’s species from the Miocene of Cuba. A PCA analysis of the correlation matrix, based on saglv, sagld, mwi and thickness (= dpv+dpd), of a sample of 25 specimens of the Pleistocene form together with the nine measured specimens of T.? palmeri presented in Cooper (1979, p. 7) suggests first the Cuban specimens are larger (higher scores on the first [size-related] eigenvector), and second the Pleistocene species is on average narrower (most Cuban specimens have lower scores on the second eigenvector that itself has a high negative loading of maximum width). Moreover, the Pleistocene species has a less-narrow ventral sulcus and less-marked carinate dorsal valves. Although Cooper did not present numerical data for the rib density of his new species, measurements on his figured specimens suggest that the rib density of the Cuban species (usually 5 or 6 ribs per 2 mm at the 5 mm growth stage) may be less than that for the Pleistocene species.
The material obtained from the Manchioneal Formation was compared by PCA ordination with specimens of Terebratulina from the ‘newer Pliocene’ within the Lucas Barrett collection (Harper, 1993); no separation was achieved along any of the eigenvectors, thus the two samples are considered conspecific. The new large sample now available from Jamaica was also compared, using PCA, with two specimens from Barbados. Separation was achieved only on the fourth eigenvector, which accounts for only 1 % of the sample variation. The two Barbados specimens have lower scores on this axis than those of the Jamaica material; since the depth of the dorsal valve has a large negative loading on this vector, the Barbados specimens have deeper dorsal valves.
Occurrence – A printing error in Harper (2002a, table 12.1) omitted the symbol ‘J’ (for Jamaica) in the ‘Pleistocene’ column for this taxon. This species is common on Jamaica at Christmas River (J3), and occurs at the type section of the Manchioneal Formation (J2), Cruikshank Bay (J1), San San Bay (J4), Folly Point (J5) and Port Maria (J6); approximately 65 shells of this species are now known from the Jamaican localities. On Barbados, the species is most common at Skeete’s Bay, Whitehaven (B1), but it also occurs at Spring Bay, Ragged Point (B3) together about 25 shells.
Suborder Terebratellidina Muir-Wood, 1955
Superfamily Megathyridoidea Dall, 1870
Family Megathyrididae Dall, 1870
Genus Argyrotheca Dall, 1900
Type species – Terebratula cuneata Risso, 1826, by original designation; from the Recent of the Mediterranean Sea.
Argyrotheca barrettiana (Davidson, 1866)
Pl. 3, figs. 1, 2.
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Material – One hundred and twenty shells of this species have been collected from localities on both Jamaica and Barbados.
Diagnosis – Medium to large, usually transverse Argyrotheca species; multicostellate with usually eight costae and costellae, increasing by intercalation up to 21 on the largest shell.
Description – Medium-sized, ventribiconvex valves of transverse to semicircular outline with maximum width either at or near hinge line or mid-valve length; cardinal extremities rounded, acute or perpendicular. Ventral valve about four-fifths as long as wide and about two-fifths as deep as long. Anterior profile with maximum convexity medianly where valve surface slightly carinate; flanks flat or weakly concave particularly near lateral margin. Lateral profile uniformly convex; umbo subdued. Ventral interarea flat to slightly curved, apsacline and about one-third valve length. Delthyrium large and open.
Dorsal valve over four-fifths as long as wide and about one-fourth as deep as long. Anterior profile with narrow sulcus originating near umbo; flanks slightly convex adjacent to sulcus, but flattened laterally. Dorsal interarea short and anacline. Ornament of strong costae and more rarely costellae; median sulcus with pair of costellae arising by internal branching within 5 mm growth stage. Four-21 ribs present on 4, 0, 1, 1,17, 3, 6, 1, 0, 2, 0, 1, 1, 3, 0, 0, 0 and 1 valves; median costae of average thickness 0.8 mm at 5 mm growth stage. Accentuated growth lamellae numbering about 3-6 per mm at 5 mm growth stage more marked on larger valves. Valve surfaces densely punctate.
Statistics –
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Discussion – The outline and profile of this species together with the style of radial ornament are most similar to those of A. barrettiana (Davidson), a Recent species, described from the Caribbean (Harper, 1993). The large amount of material now available for study suggests that the Pleistocene form is, in fact, conspecific with Davidson’s living species. A sample of 25 specimens from Jamaica was compared, by PCA of the correlation matrix, with two specimens from Barbados that yielded a comparable set of complete measurements. The two specimens from Barbados are separated on the third eigenvector, responsible for 2.5 % of the sample variation. Both specimens have higher positive scores on this eigenvector than those of the Jamaican sample; maximum width (mw) has high negative loading on this eigenvector indicating that the Barbados specimens are relatively narrower than those from Jamaica. The Barbados material is currently insufficient to form the basis for the new subspecies, suggested by the multivariate analysis.
Although Cooper redescribed A. barrettiana (Davidson) from the Caribbean Sea, he did not provide a modern diagnosis of the species. That is provided here.
Occurrence – This species is common on Jamaica at the type section of the Manchioneal Formation (J2) and Christmas River (J3), and occurs at Cruikshank Bay (J1) and Folly Point (J5); approximately 100 shells of this species are now known from the Jamaican localities. On Barbados, the species is most common at Skeete’s Bay, Whitehaven (B1), but it also occurs at Spring Bay, Ragged Point (B3) and the Arawak Cement Quarry (B4) together yielding 20 shells.