Fossil Record

The fossil record of the Myriapoda is rather patchy. While certain formations may be fairly rich in specimens, intervening periods tend to be rather poor. The Diplopoda (millipedes), to which all the Silurian and most of the Devonian records have been assigned, are the best represented in the fossil record. This is probably due more to their robust calcified exoskeleton, as well as their burrowing habits, rather than reflecting greater age or past diversity. The records seem to support the idea that independent groups of vertebrates invaded the land sequentially, starting with the herbivores which followed the earliest terrestrial plants (Rolfe, 1980).

Devonian (360 - 408 Ma)	Famennian
	Frasnian	Escuminac fm., Canada: ?Arthropleura
	Givetian	Gilboa Fauna, U.S.A.: centipedes
	Eifelian
	Emsian	Alken fauna, Germany: Eoarthropleura
	Pragian	Rhynie Chert fauna, Scotland: no Myriapoda Kampecaris tuberculata, Ayrshire
	Lochkovian	Arbuthnott Gp, Angus: K. forfarensis, A. macnicoli Kampecaris dinmorensis, Herefordshire Oban fauna: K. forfarensis, ?K. obanensis, 'Archidesmus' sp.
Silurian (408 - 438 Ma)	Pridoli	Kampecaris obanensis, Kerrara; undescribed kampecarids, Shropshire Stonehaven Gp, Kincardineshire: prob. diplopod, 'Kampecaris?' and others
	Ludlow	Necrogammarus, Herefordshire
	Wenlock	Undescribed 'Myriapods', Lesmahagow, Hagshire Hills
	Llandovery	Archidesmus loganensis, Leshmahagow

Fig. 1.1. Silurian-Devonian myriapod records arranged according to stratigraphic occurrence (Almond, 1985)

Myriapod fossils are often poorly preserved and hard to interpret. For example, identification is hampered by a lack of fossilized gonopods, which may be because the fossil forms had a primitive form of sperm transfer, or the fossils are immature animals. A similar problem is encountered when trying to establish whether differences in numbers of legs and segments are true differences.

Fig. 1.2. Reconstruction of Arthropleura, based on reconstruction from The Biology of Millipedes (Hopkins & Read, 1992) - the largest terrestrial invertebrate ever; dates from the Carboniferous. Could reach lengths of over 1m, with a breadth of 0.45m; approximately 20-30 segments. Fed on vegetable matter.

The Chilopoda (centipedes) have a sporadic fossil record from the Middle Devonian onwards (Shear et al, 1984), the Symphyla are known solely from Eocene Baltic amber (Larrson, 1978) and the Pauropoda are not represented at all. The latter two are minute forms that live in the soil and have very low chances of preservation.

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