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