Abstract
An exceptionally well-preserved specimen of the articulated rhodophyte Permocalculus , compared with P. tenellus sensu Elliott, 1955, is described from fine-grained Upper Permian limestones of the Khuff Formation of Saudi Arabia. Longitudinal medullary and sheaf-like cortical filaments extend through the uniserial series of elongate-globular, concave- and convex-terminating, interlocking segments for which they are interpreted to have functioned in articulation. The filaments tend to splay and branch laterally into the cortex where they terminate at the pores. At the terminal aperture, the filaments extend as bifurcating and possibly trifurcating branches and may serve as the origin of a new segment. Numerous elongate-globular chambers, up to five in each row and intimately involved with the filaments, are developed in the outer medulla and are considered to represent reproductive sporangia. The specimen is considered to have occupied predominantly low-energy, normal to slightly elevated salinity, shallow conditions within the subtidal regime of a lagoon.
Highlights
During quantitative analysis of thin sections prepared from core plugs taken from carbonate cores of the Khuff C Reservoir of the Khuff Formation, Saudi Arabia, an exceptionally well-preserved specimen of a calcareous alga, 10.5 mm in length, was observed in an otherwise abiotic mudstone (Fig. 1)
When microphotographs of the specimen were displayed at the 8th International Symposium on Fossil Algae, Granada, Spain, in 2003, the calcareous algal experts were keen for the specimen to be published as it displayed features never previously preserved with such detail
Micropalaeontological analysis is confined to thin-section studies because the Khuff carbonates are too well-cemented to permit disaggregation and microfossil extraction
Summary
The Khuff Formation (Steineke & Bramkamp 1952; Steineke et al 1958; Powers 1968; Insalaco et al 2006; Hughes 2008; Maurier et al 2009) represents the product of one major, but complex, marine depositional cycle that transgressed over the Arabian Platform during the Capitanian/Midian Stage of the middle Permian (Vaslet et al 2005). Shallow carbonate deposition, with interbedded siliciclastics and evaporites, continued until the Scythian/Induan Stage of the Early Triassic and the formation contains microfossil and isotopic evidence for the Permo-Triassic extinction. The calcareous alga here discussed was collected from the Khuff C carbonate, equivalent to the Duhaysan and Midhnab members (Vaslet et al 2005) according to Gaillot & Vachard (2007, Fig. 4) and dated as the Wuchiapingian Stage of the Upper Permian
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