Discovery of plate‐type scyphocrinoid loboliths in the uppermost Pr̆ídolían–lowermost Lochkovian Upper Setul limestone of Peninsular Malaysia

Abstract

Scyphocrinoid loboliths, the bulbous floats attached to the roots of a group of large Late Silurian to Early Devonian crinoids, were found within the top part of the Upper Setul limestone at two localities, in a band of limestone at Memplam Bay and in limestone blocks from a soil quarry at Guar Jentik, in northwest Peninsular Malaysia. The loboliths belong to the plate type, characterized by having plated chamber walls, few internal chambers and the presence of chamber openings near the axil of each primary root. Plate loboliths belong to species of Marhoumacrinus and Camarocrinus of the uppermost Pȓídolían to lowermost Lochkovian, and occur generally above cirrus loboliths, which are Pȓídolían only. Armoured floats are believed to have provided better protection against predators and the physical elements. These loboliths are important for correlation with other occurrences worldwide and especially within the Shan-Thai or SIBUMASU (SinoBurMalayaSumatra) terrane of southeast Asia.

Bringing planktonic crinoids back to the bottom: Reassessment of the functional role of scyphocrinoid loboliths

“…Similar “iceberg” and “snowshoe” strategies are present in some Recent mollusk and brachiopod species living on muddy bottoms (Thayer 1975). The fact that chambers of loboliths are frequently filled (at least partly) with fine sediments matching external sediment lithology may be consistent with this interpretation (e.g., Ray 1980; Lee 2005; Huber and Gibson 2007; Haude et al 2014; Donovan and Miller 2014; our data, Fig. 4).…”

The camerate crinoid Scyphocrinites Zenker in the Upper Silurian or Lower Devonian of New Brunswick, Canada

“…Further, it has a limited stratigraphic range, occurring in strata that span the Upper Silurian (Pridolian) to Lower Devonian (Lochkovian) boundary, so it is a rare crinoid that can contribute to international biostratigraphic correlation. Its occurrence varies from the gregarious (e.g., Lee 2005) to the diffuse, the latter being the case for the example that we record herein from a Silurian-Devonian boundary section at Flatlands, northern New Brunswick (Fig. 2).…”

“…Although the rarity of cross-laminated or ripplelaminated beds indicates deposition below fair-weather wave base, Wilson et al (2004) Lee (2005), in light of the pivotal research of Haude (1992), loboliths of Scyphocrinites fall into two morphological groups of broadly similar gross morphology. The primitive condition is represented by the so-called cirrus (more correctly these are inflexible radices, not flexible cirri; Donovan 1993) loboliths, formed from amalgamated branching "roots"; this group includes the .…”

The Devonian-Carboniferous Boundary At Guar Sanai, Kampung Guar Jentik, Perlis: An Updated Map And Stratigraphic Section

“…The age of the unit has been determined from conodonts and trilobites to range from Silurian (celloni-amorphognathoides Zone, Late Llandovery at its base) to the Silurian-Devonian (Pridolian-Lochkovian) boundary, which coincides with its boundary with the overlying Timah Tasoh Formation (Igo & Koike, 1966, 1968Idris, 1989;Kobayashi & Hamada, 1971;Cocks et al, 2005). Scyphocrinoids have been reported from the limestone at Pulau Langgun, Langkawi, as well as at Sanai Hill A, Kampung Guar Jentik, Perlis, which supports the Pridolian-Lochkovian age for the top of the unit (Lee, 2001;2005).…”

“…Several un-deformed sections cross the boundary between strata of different geologic periods. This includes the Cambrian-Ordovician boundary in the Machinchang Formation on the west coast of Langkawi island (Lee, 1983), the Ordovician-Silurian boundary in the Tanjong Dendang Formation on Pulau Langgun (Jones, 1981;Cocks et al, 2005), the Silurian-Devonian boundary in the transition between the Mempelam Limestone and Timah Tasoh Formation, also on Pulau Langgun (Jones, 1981;Cocks et al, 2005), and the Devonian-Carboniferous boundary at Sanai Hill B, Kampung Guar Jentik, Perlis (Hassan & Lee, 2002, 2005Hassan et al, 2014). Such boundary sections are important sites for studying geologic events of global significance that commonly are associated with geologic boundaries, e.g.…”