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The Pentland Hills sponge fauna (Llandovery, Telychian) consists of an unusual, aberrant assemblage, but of low diversity. A new specimen of a unique sponge, Eoghanospongia carlinslowpensis gen. et sp. nov., is described from the classic locality of R82. The mushroom-shaped, probably stalked body (peduncle attachment to body not exposed) resembles that of some living rossellids, especially Caulophacus. The sponge also shows prominent projecting pentactins and monaxon derivatives – a spicule type diagnostic of the Rossellidae among living taxa, albeit in a robust form not described from extant sponges, including Caulophacus or other pedunculate lyssacinosidans. Certain attribution to the Rossellidae is not possible from the single specimen, largely because of weak preservation of the primary spicule skeleton, but no other fossil or modern sponges show any significant similarity to it. Although similarly early relatives of the Rossellidae have recently been described from elsewhere, the new sponge is even more unexpected in being from a shallow-water environment, making the absence of rossellids through the rest of the Palaeozoic much more problematic.
Some 40 brachiopod species are known from the localities of Kilbucho and Wallace’s Cast in the Kirkcolm Formation in the Northern Belt of the Southern Uplands of Scotland. The fauna is diverse despite the relatively small numbers of brachiopod specimens (c. 180) available for study. Much of the fauna was transported downslope and is locally preserved in obtrution deposits. It represents a broad census of outer shelf and upper slope palaeocommunities around this part of the Laurentian margin during the early Katian, and is dominated by relatively small plectambonitoid brachiopods. When compared with other circum-Iapetus assemblages, the brachiopods from the Southern Uplands compare most closely with those from the Bardahessiagh Formation, Pomeroy, Northern Ireland, rather than with adjacent, well-known faunas from the Girvan district, SW Scotland. These new data suggest that this part of the Southern Uplands was located in closer proximity to Pomeroy than Girvan, and located in deep-water environments similar to those in the upper parts of the Bardahessiagh Formation.
Comparisons of the Caradoc assemblages with North American biofacies indicate that the Bardahessiagh Formation was deposited during a transgressive regime, which peaked with the presence of a typical Sericoidea association (member (II)). These diverse and exceptionally preserved faunas lived below the storm-wave base. The assemblages also contained a shallower water brachiopod component typical of transition zone environments or above, which may have been transported during periods of instability. A deep-water regime (BAs 4 to 4–5) through the Rawtheyan occurs with the deposition of the Killey Bridge Formation, which yielded a diverse brachiopod fauna including Bimuria, Chonetoidea and Christiania. The Rawtheyan assemblage also contains a shallower water component. Representatives of the deep-water Proboscisambon assemblage occur in middle parts of the Tirnaskea Formation. This distinctive low-diversity assemblage yields small, thin-shelled brachiopods including Dedzetina, Sericoidea, Protozyga and Proboscisambon. The upper parts of the Tirnaskea Formation yielded the low diversity, shallow water (BA 3) Hirnantia fauna, which is characterised by the presence of Eostropheodonta, which is a key form of the fauna, Dysprosorthis and the absence of Hirnantia. As a whole the changing brachiopod biofacies monitor environmental fluctuations, on part of the Laurentian margin, driven mainly by eustatic and tectonic events.
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