Raiders of the Lost Shark 27/10/2007

Camera (mostly) and setups by Tarquin, flash and modelling and other camera by Peter Wilton-Jones, edits and gallery effects by Tarquin. If you would like to use any of the fossil pictures for research purposes, please get in touch, and I can send you the originals in full quality. The hands and fingers are to give an idea of scale, without something so artificial as a ruler, which can really spoil caving pictures.

Raiders is an often overlooked passage, just one of the many side passages on the Round Trip. However, it is one of the most comfortable passages that Ogof Draenen has to offer, being mainly easy walking, and within easy reach of the entrance. On top of that, it boasts two features that make it stand out; its piles of bat guano are - along with those in Canyon Passage - the largest in the British Isles, and it has the most impressive collection by far of large fossils still in their natural setting.

The fossils are far more abundant than those in the Entrance Series, and in far better condition as well, showing fine detailed textures. The majority are ctenacanthus dorsal spines, but a few are probably gyracanthus pectoral or dorsal spines, as well as some psammodus tooth plates. A few others are unknown to me, and I welcome any help you can offer in identifying them. Ctenacanthus, gyracanthus and psammodus were sharks living around 300 million years ago.

Considering that all of these fossils are encountered within around only 1 km of passage, it begs the question of how many are there, and have not been found? In total, there were well over 50 that we saw, as well as many more tiny unidentifiable fossils. This number includes only those intersected by the walls of the passage, so the total number in the area must be staggeringly high. What happened here 300 million years ago to kill so many sharks in such a short timespan? Did the sea levels drop and leave them stranded? This part I cannot answer.

1. Botryoids on the roof of Raiders passage
2. The first fossil, not very well defined, but at least showing the blood vessel holes
3. The longest known fossil in Raiders Passage, with the upper fossil being 25 cm (10 inches) from end to end (the right end of it enters, then re-emerges from the rock) - note that the longer fossil has a different cross section
4. Unconformity in the roof of Raiders, causing one side of the passage to be almost white, while the other is brown or dark orange
5. The third fossil, showing the normal cross-sectional shape that helps identify them
6. Fossil showing some of the textured surface ridges - one of the other hints that helps identify the fossils
7. Shells making up the limestone
8. Swirling shell
9. The unconformity has now caused the colour bands to swap sides
10. A fossil trying to hide in the roof
11. Hexagonal calcite crystals in a small alcove - the largest is about 1 cm in diameter
12. Textured passage walls
13. A fossil with a very different shape, clearly not a dorsal or pectoral spine, but what is it?
14. Another differently shaped fossil - it could be the tip of a dorsal spine - many other fossils like this exist, ranging from a few mm across, to this example about 2 cm long - most do not seem significant enough to deserve a photograph, but perhaps they are more important than I understand (after all, sharks have a cartilaginous skeleton, and only the bony dorsal spines, pectoral spines, and teeth of these proto-sharks should be preserved - is this something else?)
15. Back to the more normal design
16. Small calcited holes, which could possibly be tiny geodes
17. The broken remains of a spine
18. Porous textured cross section
19. A very long example, about 14 cm (5.5 inches) long, showing some significant distortion
20. Swirling shell
21. Another fossil spine, with its vertical surface decorated by a mouldy bat dropping - exactly how a bat managed to eject its dropping sideways, and cause it to stick to a vertical surface, is something for your own imagination to decide
22. Spine hidden in an alcove
23. Another completely different shaped fossil, almost rectangular, with a unique texture, and visible fluting towards its lower surface - perhaps this is a cross-section through a tooth plate
24. One of the largest piles of guano in the British Isles - this is lesser horseshoe guano, showing distinct towers where the bats have chosen the exact same spot, year after year - most of the guano is quite old, and does not relate to current roosting bats, probably dating to when there were more natural entrances to the cave system
25. Another very large pile of guano
26. A fossil hiding in the roof, probably originally horseshoe-shaped, but since broken when the limestone was forming
27. Another porous texture
28. A beautifully textured surface, clearly different to the other fossils - it seems quite reminiscent of the large fossil in the Entrance Series, but has much more defined surface nodules - can you identify this fossil?
29. A small fossil tucked in an alcove
30. Two pieces of a large fossil in the alcove
31. Fossil showing a blood vessel hole
32. Beautiful cross-section, showing several blood vessel holes, and the characteristic shape
33. Fossil with a lot of erosion damage
34. Slightly muddied (naturally, not by humans) example
35. An immaculately preserved tooth plate - unlike what we perceve as sharks today, proto-sharks such as psammodus did not have pointed teeth - instead, they had grinding plates which were used for crushing, similar to molar teeth
36. Detail of the tooth plate texture, with the characteristic dimples that suggest this was probably a psammodus tooth plate
37. Internal construction of the bone fibres
38. Large protruding spine
39. Surface ridges of a spine
40. Muddied fossil in an alcove - this continued on the other side of the alcove, and would have been a very large example at one point before the erosion removed it
41. Spine fragment
42. Another strangely flat fossil - perhaps this is a gyracanthus shoulder spine
43. Textured fossil in a bedding, almost indistinguishable from the thin shale layer in the bedding
44. Tucked into a very narrow rift in the roof
45. Bone fragment
46. Another beautiful surface texture, showing the surface ridges running almost end to end, which suggests this was a ctenacanthus dorsal spine - if this were a gyracanthus spine, most of the ridges would run across it from side to side on a slant instead, and the cross section would be more rounded, with a smaller U-shaped indent
47. Spine fragment
48. Gypsum crystals in an alcove, with another fossil on the right
49. Lumpy calcite formations that appear to have formed under water
50. Gypsum crystal at the start of the fault
51. Spine high up on the wall
52. Spine fragment
53. Though not the longest at 20 cm long, this is by far the largest of all the fossils in terms of volume and exposed surface
54. The surface texture shows that this was probably a ctenacanthus dorsal spine, and represents an extremely large shark for it species
55. The fault contains the largest part of Raiders Passage
56. Another beautiful surface texture
57. High on the wall of the fault, but unfortunately positioned at traversing height, this fossil could do with some cleaning
58. Another tooth plate - there was a third one near here whose surface had been eroded badly, and a possible fourth that may have just been a pebble
59. Another large fossil, about 20 cm long, passing through a rock flake at the end of the fault
60. In the chamber in the bedding opposite the entrance to Raiders Passage is the second of the two largest fossils, being 25 cm (10 inches) long, with a very detailed surface
61. Another fossil near the previous one
62. Deep anastomosis corroded into shapes that look like canine teeth
63. The 4 m roped climb in the Entrance Series (yes, we're on our way out now)
64. Making the climb look harder than it is
65. The worst part of the Entrance Series, which slopes sideways, starting as a single hole with a waterfall, and ending as a figure-of-8 shaped hole where only the drier side is wide enough for most people to get through
66. And the second worst part, a low crawl in the stream at the top of the hole - still, at least when you get here, you are nearly out