| Fauna & Flora |  |
| Fauna & Flora | |
The Ludlow Bone-beds contain a
mixed aquatic and terrestrial fauna including material from the
oldest known terrestrial ecosystem (Dunlop, 1996). Within the
bone beds the thin Lagerstatte bed 0.2m above the Ludow Bonebed
senso stricto contains the highest abundance of terrestrial
organism remains. The terrestrial fauna so far discovered contains
vascular plant material (Cooksonia), two types of centipede,
kampecarid myriapods, an arthropleurid, a trigonotarbid (Palaeotarbus
jerami) and numerous arthropod fragments that are unidentifiable.
Palaeotarbus jerami
The Ludlow Bonebed is most widely know for yielding a specimen of a genus of trigonotarbid known as Palaetoarbus or 'The Burnt Cornflake' on account of its preservation. Trigonotarbids are spider-like arachnids that are believed to have originated in the late Silurian until they became extinct in the early Permian (Dunlop, 1996). Palaeotarbus jerami described by Dunlop (1996) posesses a triangular head region, or prosoma, and a rounded, segmented posterior region called the opisthoma. It is these features that principally identify this specimen as a trigonotarbid. The carapace of Palaeotarbus jerami is folded and pitted though ten sternites (segmental divisions of the opisthoma) are discernible. The ventral surface (not shown) exhibits two eye-like features positioned medially with two small notches anterior to the eyes. Unlike the Carboniferous trigonotarbid Trigonotarbus johnsoni, Palaeotarbus does not posess a median ridge on the prosoma. The triangular prosoma also differs from the Devonian palaeocharinid trigonotarbids from Rhynie, Scotland and Gilboa, USA which posess a box-like carapace. This makes Palaeotarbus remniscent of the Trigonotarbidae family and not the Palaeocharidinae family. Evidence of appendages is poor though two anterior coxae (limb bases) and an incomplete limb consisting of a partial femur to the teleotarsus is present compressed against the opisthoma.
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Palaeotarbus jerami, Silurian, Pridoli, Ludford Lane, Shropshire. Scale bar represents 0.5mm. Photograph courtesy of Dr S.J.Braddy. Rhynie trigonotarbid reconstructions (Dunlop. J., University of Aberdeen). |
Other arthropod cutilcle fragments
Several fragments of arthropod limbs (podomeres) attributed to a terrestrial fauna have been found in the Ludford Lane Bonebed deposit. These can be differentiated into two types of centipede (Jeram et al. 1990).
The most common type of podomere are referred to as 'sawblade' podomeres and possess prominent carinae (small keel-like ridge structures) with infrequent setae (hair-like protrusions) very similar in ornament to material found at Gilboa, USA.
Less common are limbs that possess more setae than the sawblade type. One specimen has been found that is semi-complete bearing the femur, tibia, tarsus and a terminal claw. Part of the femur and tibia possess a large claw-like appendage.
Kampecarid myriapods
Kampecarids have features similar to millipedes though do not have as many sternites as the Diplopods (millipedes). They are uniramous (each segment has one pair of legs) rather than biramous as in the Diplopoda and may have possibly been aquatic (Almond, 1985). The vast majority (70%) of the cuticle fragments recovered from the Ludford Lane locality is featureless material belonging the kampecarids (Jeram et al., 1990) though individual and articulated segments have been recovered.
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Flora
Cooksonia
The Ludford Lane locality has yielded the only recorded ocurrence of the early land plant Cooksonia from Ludford Lane despite being a recognised, widely spread Late Silurian plant. It has a simple morphology consisting of a series of biurcating stems with epidermis and stomata and xylem vessel system. The stems are topped by sporangia whereas the rootsystem is believed to have been a simple rhizome.
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Cooksonia caledonica |
Jeram et al. (1990) have also identified a birfucating rhyniophytoid, Hostinella, from the material that they recovered and interpreted the axes (stem) as being sterile (not possessing sporangia).
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