Vertebrate biostratigraphy of the Ludlovian Hemse Beds of Gotland, Sweden

Abstract

Samples from every unit of the Hemse Beds were studied for vertebrates, and five successive vertebrate faunas were distinguished: (1) The thelodont Phlebolepis ornata, occasionally occurring with other thelodonts, ranges from Hemse Beds unit b and at least up into beds corresponding to the lower part of unit c (Late Eltonian to Early? Bringe-woodian); (2) A pure thelodont fauna with “Logania” martinssoni, Phlebolepis elegans, Thelodus carinatus, and T. parvidens (only in the upper part) continues unmixed from the older Hemse Beds and up into the base of the younger beds in the central area (Bringe-woodian to Leintwardinian); (3) The acanthodian Nostolepis striata dominates in the lower part of the Polygnathoides siluricus conodont Zone (Leintwardinian) in the younger Hemse Beds. This fauna also includes the cyathaspid Archegonaspis lindstroemi, the actinopterygian? Andreolepis hedei, the acanthodian Gomphonchus sandelensis and the thelodonts of the second fauna; (4) The upper part of the P. siluricus Zone is dominated by G. sandelensis; (5) The uppermost Hemse Beds (Late Leintwardinian) are characterized by the appearance of the thelodont “Logania” cuneata?

Key Words:

• Vertebrata
• biostratigraphy
• Silurian
• Ludlovian
• Gotland