Graptolites:
Graptoloids: Colonial plankton with an organic exoskeleton consisting of a series of tubes (thecae) growing out along branches (stipes), from a conical larval stage (sicula). Dendroids: Multi-branched benthic or pseudoplanktic forms with a bush-like habit.
In general, graptolites are best preserved in fine sediments, ideally with limited sea-floor (benthic) communities that could otherwise destroy them. In shallow water sediments they are usually rare or broken. Even in fine sediments, details such as spines are often lost by damage or decay. They are often preserved as organic films that show little structure, although sometimes they are preserved in three dimensions, usually following infill of the colony by pyrite. When flattened, the orientation of flattening can be critical to identifying them, and apertural views are almost impossible to do anything with.
Identifying graptolites at species level is a very specialised task. Often it relies on measurements, but these are variable within each population. In particular, the two Didymograptus species are extremely variable, evolving quite spectacularly through the sequence, and the pattern of budding of the first three thecae is essential to identify them reliably. In general, the early growth stages are the most useful for identification, but even so, several specimens are often needed to be certain.
There is a good chance that additional species will be discovered. This is particularly true of bushy, benthic dendroid graptolites, which have been so poorly studied from this area that almost every new specimen is likely to be a new species. They tend to be rare, but if you find one, there are likely to be diverse others at the same site. Key features to look for are the shape of the thecae in profile (look at the edges of the colony, where the stipes are in side view), whether the branches are joined by dissepiments (cross-branches), and the branching pattern. The dendroids will probably be studied in the relatively near future, so any collection of specimens is especially timely.
[2]Acanthograptus sp. Approx.~5 mm.
[3]Archiclimacograptus? sp. Up to ~ 35 mm long.
[1]Amplexograptus confertus. Up to ~ 15 mm long.
[4,5]Climacograptus brevis brevis. Up to ~ 20 mm long.
[3]Climacograptus sheldoni. Up to ~ 15 mm long.
[3,4,5]Cryptograptus tricornis. Up to ~ 20 mm long.
[1]Dendrograptus sp. A. Colony up to 20 mm.
[2]Dendrograptus sp. B. Colony up to 10 mm.
[5]Dendrograptus sp. C. Colony up to 15 mm.
[5]Dendrograptus sp. D. Colony ~ 10 mm.
[5]Dendroid gen. et sp. nov. Colony ~ 40 mm.
[2]Dendroid indet. A. Colony ~ 7 mm.
[3]Dendroid indet. B. Colony ~ 5mm.
[5]Dendroid indet. C. Colony ~ 7 mm.
[5]Dendroid indet. D. Colony ~ 8 mm.
[2]Desmograptus sp. A. Colony up to 15 mm.
[5]Desmograptus sp. B. Colony up to 20 mm.
[5]Desmograptus sp. C. Colony up to 20 mm.
[5]Dicellograptus cambriensis. Stipes up to 60 mm.
[5]Dicellograptus geniculatus. Stipes up to 40 mm.
[5]Dicellograptus intortus. Stipes up to 30 mm.
[5]Dicellograptus salopiensis. Stipes up to 50 mm.
[5]Dicranograptus brevicaulis. Stipe up to 40 mm.
[1,2,3]Didymograptus (Didymograptellus) cf. amplus. Stipes up to 30 mm long.
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[1,2,3]Didymograptus (Didymograptus) artus/murchisoni. Stipes uo to 30 mm long.
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[3]Diplograptus decoratus. Up to 50 mm long.
[2,3,4]Diplograptus foliaceus. Up to 50 mm long.
[3]Glyptograptus sp. Up to 25 mm long.
[4,5]Hustedograptus cf. teretiusculus. Up to 60 mm.
[2]Lasiograptus? aff. floweri. Up to 15 mm.
[1]Lasiograptus? floweri. Up to 30 mm.
[5]Leptograptus validus validus. Stipes up to 100 mm.
[5]Nemagraptus cf. subtilis. Up to 50 mm.
[4?,5]Nemagraptus gracilis. Up to 150 mm diameter, with multiple spirals, but more normally ~ 30 mm.
[1]Prolasiograptus retusus, up to 25 mm.
[3]Pseudocallograptus? sp., up to 25 mm.
[3,4]Pseudoclimacograptus angulatus sebyensis. Up to 30 mm, usually ~ 15 mm.
[5]Pseudoclimacograptus modestus. Typically ~ 15 mm.
[4]Pseudodendrograptus sp. Fragment only 2 mm wide; stipes 0.5 mm wide.
To be drawn:
[3]Climacograptus sp. (poss. C. scharenbergi)
[4,5]Dicranograptus irregularis
[3]Diplograptus priscus
[1]Eoglyptograptus sp., from the oldest graptolitic beds in the inlier
[3]Orthograptus? sp.
[1]Pseudoclimacograptus? sp., from the oldest graptolitic beds in the inlier
[5]Reteograptus
sp.
[1] Clonograptus? sp.; single specimen, reported by Brian Beveridge.
