Myriapoda henrik Enghoff Natural History Museum of Denmark




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MYRIAPODA
Henrik Enghoff

Natural History Museum of Denmark (Zoological Museum)


2005
<page and fig. references, “RFB”, refer to

Ruppert, Fox & Barnes: Invertebrate Zoology, 7th. ed. 2004.>


There are four classes of Myriapoda, viz. Chilopoda (centipedes, DA: Skolopendre), Diplopoda (millipedes, DA: Tusindben), Pauropoda (pauropods, DA: Pauropoder) and Symphyla (symphylids, DA: Symfyler).

THE POSSIBLE MONOPHYLY OF MYRIAPODA AND THE RELATIONSHIPS BETWEEN THE MYRIAPOD CLASSES
(Also read “Phylogeny of Tracheata” in RFB p. 718-720”)
Myriapod phylogeny is unsettled, but possibly the four myriapod classes plus the class Hexapoda constitute a monophyletic 'subphylum' Uniramia, also known as Atelocerata and Tracheata.
The presence of numerous legs, which has given the myriapods their name, is obviously a symplesiomorphy. Within the framework of a monophyletic Uniramia, several sister-group relationships have been proposed:


  • (Hexapoda) – (Myriapoda)

  • (Hexapoda) – (Symphyla)

  • (Hexapoda) – (Chilopoda)

  • (Chilopoda) - ((Hexapoda) – (Symphyla+Pauropoda+Diplopoda))

The following traits have been mentioned as possible synapomorphies for the four myriapod classes, i.e., as arguments for a monophyletic group Myriapoda (numbering continued from first part of compendium):




  1. No mandibular abductor muscle; abduction of mandibles effectuated indirectly by the movable anterior tentorium (Fig. 1)

  2. Median eyes never present (in Crustacea, the median eyes are represented by the nauplius eye, in Hexapoda, they are represented by the ocelli .

  3. No perforatorium in the spermatozoa (Fig.2: "1-laget acrosom" (one-layered acrosome), in contrast to the two-layered acrosome in "Insecta" which is considered to be the original state)

All these have been considered reductional characters and therefore of limited value. The absence of an abductor muscle may, however, be primary, i.e., a plesiomorphy, and the same may be true of the movability of the tentorium (Klass & Kristensen i Deuve ed., 2000). The presence of the anterior tentorium in itself appears as an apomorphy immediately below the myriapod level, i.e. as an apomorphy for Uniramia.


The characters invoked in favour of the hypothesis of a sister-group relationship between Symphyla and Hexapoda are possibly symplesiomorphies or convergencies:


  1. Three pairs of buccal appendages (mouthparts) (RFB: fig. 20-7B-C, p. 710). Ruppert & Barnes follow Manton in rejecting this similarity based on differences between the buccal appendages of symphylids and hexapods: this suggests that the presence of three pair of buccal appendages could be convergent.

  2. Second pair of maxillae forming a labium (‘lower lip’). This character, too, may be regarded as a convergence. The morphological interpretation of the ‘lower lip’ in Diplopoda and Pauropoda is still under debate (cf. below).

The basis of the hypothesis of a sister-group relationship between Chilopoda and Hexapoda is tenuous:




  1. In both groups the gonopores are located at the posterior end of the body, unlike the situation in Diplopoda, Pauropoda and Symphyla (‘Progoneata’, cf. below) where they are placed near the anterior end. Out-group comparison (with Crustacea and Chelicerata) is of no help here, but the posterior gonopore is most likely the original condition within Uniramia and thus cannot be used as an argument in favour of a Chilopoda-Hexapoda sister-group relationship.

There are several similarities between Hexapoda on the one hand, and Diplopoda+ Pauropoda+Symphyla on the other. They are all quite subtle, and none is persuasively synapomorphic. One example is:




  1. The eversible coxal sacs which are found in Symphyla (RFB: p. 711), certain Diplopoda (Penicillata, Colobognatha, Nematophora) and certain (‘primitive’) Hexapoda. The coxal sacs are probably symplesiomorphic and have become lost in Chilopoda, Pauropoda, many Diplopoda and most Hexapoda).

Wheeler et al. (1993) analysed arthropod relationships using one morphological and two molecular (DNA) data sets. Their analysis included Diplopoda and Chilopoda (but not Symphyla and Pauropoda) as well as numerous groups of Hexapoda, Crustacea and Chelicerata. Both molecular data seta indicated that Diplopoda and Chilopoda were more closely related to each than to any other the other included groups and thus support the hypothesis of myriapod monophyly. (The analysis of the morphological character set – a character set with several flaws – did not resolve the relationship between Diplopoda, Chilopoda and Hexapoda.)


It was suggested above that Chilopoda differ from the other myriapod classes. The latter, viz., Diplopoda, Pauropoda and Symphyla, together constitute the group Progoneata. This name (‘pro’: in front, ‘gon-’: having to do with sexual organs) refer to a possible synapomorphy between the three classes, viz.:


  1. The gonopore is placed anteriorly on the body (cf. the discussion under character 6).

Other possible synapomorphies between the three classes (i.e., autapomorphies for Progoneata) are:




  1. clypeus and labrum are fused (in Chilopoda and Hexapoda the labrum is separated from the clypeus by a suture and is ± movable. RFB: fig. 20-2C, p. 705, shows the clypeus in a chilopod; the labrum is not visible, but is placed in ’the black hole’ between clypeus and first maxilla.

  2. The body segments have ventral apodemes (Fig. 3). In Diplopoda and Pauropoda these are the tracheal apodemes (see below). In Symphyla there are no tracheae connected with the apodemes – the tracheae may be secondarily reduced like in most Pauropoda.

  3. Trichobothria basally swollen. Trichobothria are a special type of sensory hairs which are set in a complicated socket. Trichobothria occur in numerous groups of terrestrial arthropods (especially in arachnids, but unfortunately not in Chilopoda), but in Progoneata the trichobothria are characterised by having the base of the hair swollen (Fig. 4). In Symphyla there is one such pair of trichobothria in the posterior end of the body (RFB: fig. 20-7D, p. 710). In Pauropoda there are five pairs laterally on the body (RFB: fig. 20-13, p. 718). In Diplopoda trichobothria are known only from the Penicillata where there are 3 pairs on each side of the head. In spite of the different body parts where the trichobothria are situated, the characteristic structure of the progoneate trichobothria be regarded as apomorphic.

Within Progoneata, Symphyla are sister-group to Diplopoda + Pauropoda. Synapomorphies between Diplopoda and Pauropoda include:




  1. Immediately behind the mandibles there is a complex ‘lower lip’ (Fig. 5), the composition of which is controversial. Some regard it as a composite of the two pairs of maxillae, others maintain that it is formed exclusively by the first pair of maxillae, the second pair being entirely suppressed; at least part of the dorsal part of the second maxillary segment is represented by the ‘collum’ (RFB: fig. 20-9, p. 712, fig. 20-13, p. 718). Cf. character 5 above.

  2. In both groups, the spiracles are situated on the sterna, near the leg bases (RFB: fig. 20-10B, p. 713). Both groups have tracheal apodemes associated with the spiracles (cf. character 10). Tracheae have arisen several times independently in arthropods. The ventral system in Diplopoda + Pauropoda undoubtedly represents one ‘invention’ of tracheae, whereas it is more doubtful if the lateral system in non-scutigeromorph centipedes (RFB: fig. 20-2E, p. 705) is homologous with that of Diplopoda + Pauropoda. The tracheal system in Symphyla (RFB: fig. 20-7, p. 710) is even more dubious in this respect. The dorsal tracheal system of scutigeromorph centipedes (RFB: fig. 20-2B, p. 705) certainly represents an independent ‘invention’.

Based on the characters discussed above, the relationships of the myriapods can be illustrated as in the cladogram, Fig. 6.


Alternative relationships between the myriapod classes have been suggested. Fig. 2 thus suggests a sister-group relationship between Pauropoda and Chilopoda, based exclusively on the morphology of spermatozoa; this similarity is probably a symplesiomorphy. Symphyla + Chilopoda have also been regarded as sister-groups, mainly because both classes lack limbs on the last two body segments. Balanced against the autapomorphies for Progoneata suggested above, this character is, however, not convincing.
CLASS CHILOPODA – CENTIPEDES (DA.: SKOLOPENDRE)
RFB: 703-710.
The numbers of apomorphies in this section refer to Fig. 7.
Chilopoda autapomorphies:


  1. First pair of body limbs transformed into poisons fangs (‘forcipules) (RFB: fig. 20-2, A, C, p. 705).

  2. Second maxilla in the embryo provided with an ‘egg-tooth’.

  3. Nucleus of spermatozoon spiral-shaped


Systematic review of Chilopoda – centipedes
More than 3000 species of centipedes have been described. Thirty-two species have been recorded in Denmark.

Order Scutigeromorpha


Ca. 130 species from the warmer parts of all continents. Easy to recognize by the 15 pairs of extremely long, multi-segmented legs, and equally extremely long antennae. Composite eyes which may be inherited from the common ancestor of all centipedes although some structural details suggest that the eyes of scutigeromorphs may be derived from single eyes of the type found in Lithobiomorpha and Scolopendromorpha; in the latter case the secondarily composite eye in Scutigeromorpha is an autapomorphy. Certain autapomorphies include:


  1. The dorsal spiracles (RFB: fig. 20-2B, p.705)

  2. The strongly sub-segmented tarsi


Scutigera coleoptrata is common in southern Europe and has been found occasionally in houses in Denmark (introduced).

Order Lithobiomorpha


Ca. 1500 species from all parts of the World. Fifteen pairs of walking legs like in Scutigeromorpha, but the tarsi are not multi-segmented, and the eyes are not composite; the spiracles are lateral and are present only on some of the segments. An autapomorphy is:


  1. The single testicle (RFB: fig. 20-4, p. 707). Two testicles are formed in the embryo, but one is later reduced. (Scutigeromorpha have paired testicles; see below on Scolopendromorpha and Geophilomorpha, character 12).

A further, possible autapomorphy is:




  1. coxal pores (Fig. 8, cf. also below) on at least two pairs of legs, not only on the last pair as in Scolopendromorpha and Geophilomorpha.


Lithobius forficatus (to 3 cm long) is extremely common in Denmark, like several smaller species of the same genus. Lamyctes emarginatus is the only myriapod known from Greenland; it is parthenogenetic and is also known from Denmark.

Order Craterostigmomorpha


Only one species, Craterostigmus tasmanianus, from Tasmania and New Zealand. Hatches from the egg with 12 pairs of legs, the adult number of 15 pairs is reached after one moult; the number of leg-pairs is certainly a symplesiomorpy with the two orders above. C. tasmanianus superficially resembles a Lithobious.

Order Scolopendromorpha


Ca. 500 species in all parts of the World, mainly in warm regions. They resemble Lithobiomorpha superficially, but they have 21 or 23 pairs of walking legs. An autapomorphy is:


  1. The tergum of the poison fang segment is fused with that of the following segments (that carrying the first pair of walking legs). (The fused tergum is seen in RFB: fig. 20-1A, p. 704 as a trapezoid plate just behind the head).

Family Scolopendridae: four eyes on each side of the head. The very large centipedes belong here, genus Scolopendra and others in the tropics and subtropica including southern Europe.


Fam. Cryptopsidae: no eyes. Cryptops hortensis (2-3 cm) in Denmark. Scolopocryptops (= Otocryptops).

Order Geophilomorpha – Da: jordskolopendre


Ca. 1000 speices in all parts of the World. From 29 to almost 200 pairs of legs. No eyes. Good autapomorphies include:


  1. the earthworm-like burrowing technique (RFB: 707)

  2. the constant number of 14 antennal articles. In the other orders, the number is large and variable.

The high number of legs and the lack of eyes are other possible autapomorphies.


Several families, a dozen species in Denmark including Geophilus carpophagus, which is bioluminescent (glows in the dark) and occurs in old houses, and Strigamia maritima, which is sometimes abundant under seaweed on the beach.

Centipede phylogeny
The phylogeny of centipedes has been subject of much debate. The discussion illustrates very well the difficulties with deciding which characters are original, plesiomorphic, and which are derived, apomorphic. The Geophilomorpha have been regarded as sister-group to the other centipede orders, and so have the Scutigeromorpha. The class has also been divided into two groups: Anamorpha (= Scutigeromorpha + Lithobiomorpha) and Epimorpha (= Scolopendromorpha + Geophilomor­pha). Based, among other things, on increased knowledge of the fifth order, Craterostigmomorpha, Dohle (1985) and Shear & Bonamo (1988) were able to present a convincing phylogenetic analysis, according to which relationships are as shown in Fig. 7.
The group Anamorpha was named after the mode of postembryonic development in its members, viz., hemianamorphosis: The juveniles hatched from the egg have 4 pairs of legs (excluding the poison fangs) in Scutigeromorpha, 6-7 pairs in Lithobiomorpha. The adult number (15 pairs) is gradually attained during growth, and when it has been reached, no new leg-pairs are added during succeeding moults. Hemianamorphosis occurs in all Pauropoda and Symphyla and also in primitive Diplopoda; this character is thus a clear symplesiomorphy for the members of ‘Anamorpha’.
Several synapomorphies are shared by Lithobiomorpha, Craterostigmomorpha, Scolopendromorpha and Geophilomorpha, including:


  1. the head is flattened

  2. the tentorium is reduced in a characteristic way

  3. the sternum and coxae of the poison fangs are fused to a coxosternum (RFB: fig. 20-2, p. 705, “coxosternite plate of forcipule”). This is clearly apomorphic, since the poison fangs are derived from normal walking legs

  4. the last leg-pair at least has coxal organs of a characteristic structure. They open to the surface through coxal pores (Fig. 8) and probably serve a water-regulatory function

  5. the spermatophore is placed on a web produced by a spinneret in the rear end of the male (RFB: fig. 20-6A p. 709).

Craterostigmomorpha, Scolopendromorpha og Geophilomorpha share further synapomorphies:




  1. eggs and young juveniles are protected by parents (RFB: fig. 20-6C, p. 709)

  2. juveniles hatch with the full (or almost full) adult number of segments and legs.

Scolopendromorpha og Geophilomorpha finally share the following synapomorphies:




  1. juveniles hatch with full number of adult number of segments and legs

  2. the testicles are fusiform, with vasa efferentia originating from both ends (Fig. 9, cf. RFB: fig. 20-4, p. 707)

  3. tracheae from different segments anastomose

  4. there is no median suture on the coxosternum (cf. character 6)

  5. there is a direct articulation between first and fourth article of the poison fang’s telopodite (Fig. 10, cf. RFB: fig. 20-2C, p. 705).

One character is in strong conflict with the cladogram, Fig. 7, viz., the heterotergy. In Geophilomorpha all terga are of similar size (homotergy). In the other orders there is a more or less pronounced alteration between short and long terga: heterotergy. In RFB: fig. 20-1, p. 704, the heterotergy is clearly seen in Lithobius, not so clearly in Otocryptops. In Scutigera the short terga are entirely hidden under the long ones. Intuitively one would believe homotergy to be original, heterotergy thus being a synapomorphy for all centipedes except Geophilomorpha. Balanced against characters 4-15 above, the heterotergy, however, must be regarded as convergent or plesiomorphic, in the latter case the homotergy in Geophilomorpha would be secondary.


Spermatological evidence (Jamieson 1987) is also partly in contrast with the phylogeny advocated above. Spermatology does support the sister-group relationship between Scutigeromorpha and the rest, but also provides a possible (but not very well founded) synapomorphy between Lithobiomorpha and Geophilomorpha, which is in conflict with characters 11-15 above.

CLASS SYMPHYLA – SYMPHYLIDS, DA.: SYMFYLER
RFB: 710-711.
The large spinnerets in the posterior end may constitute an autapomorphy for symphylids. It is, however, uncertain, whether the spinnerets are homologous with the cerci of Hexapoda (the cerci of some Diplura have spinning glands like the spinnerets of Symphyla). The position of the two trichobothria is another possible autapomorphy (but not the trichobothria by themselves, see character 18 in the chapter "The possible monophyly of Myriapoda and the relationships between the myriapod classes"). Also, the extra tergites may constitute a symphylidan autapomorphy although their number is variable.
The styli mentioned by RFB (p. 711) (Fig. 11) also occur in some apterygote hexapods: Archaeognatha and Diplura. Also, stylus-like structures are found in the diplopod subclass Penicillata, and in Pauropoda.
About 160 species of Symphyla have been described. Four species have been found in Denmark. Scutigerella immaculata – one of the largest symphylids – is very common in humid forest soil and similar places in Denmark.

CLASS DIPLOPODA – MILLIPEDES, DA.: TUSINDBEN
RFB: 711-717.
The numbers of apomorphies in this chapter refer to Fig. 12.
Good autapomorphies for millipedes are:


  1. diplosegments (RFB: 713).

  2. spermatozoa without a flagellum (Fig. 2)

  3. antennae with 8 articles, with four large, cone-shaped sense organs on the tip (Fig. 13)

There are 16 orders of millipedes in the current classification, a clear example of ‘taxonomic inflation’. Looking at the degree of distinctiveness and recognisability it is rather the superorders of millipedes that may be compared with insect of arachnid orders.


About 10,000 species of millipedes have been described; 42 species are known from Denmark.

SUBCLASS PENICILLATA – pincushion millipedes, da.: penseltusindben


easily recognized by the autapomorphic character:


  1. tufts of bristles along the sides of the body and in the posterior end

About 100 described species from all regions. Only a few mm long, the pincushion millipedes exhibit many primitive traits and seem not to have departed very much from the millipede ground-plan. They thus have retained trichobothria (cf. character 18 in the section on myriapod relationships), their cuticle is not calcified, and the number of legs is relatively low: 11-17 pairs in adults. Terga, pleura and sterna are independent (except that the terga are fused into twos [diplosegments]). No legs are modified for copulation. Sperm transfer happens indirectly: the male deposit spermatophores which are later taken in by the female (RFB: fig. 20-12E, p. 717).


It has recently been suggested (Kraus & Brauckmann 2003) that the Penicillata are closely related to the extinct Arthropleurida, giant (more than 1m, perhaps even more than 2m) myriapods from the Devonian, Carboniferous and Permian periods.
One order, Polyxenida. One species in Denmark, Polyxenus lagurus. See RFB: fig. 20-8B, p. 712. P. lagurus is often, but not always parthenogenetic, and it is this species which RFB (p. 717) refers to.

SUBCLASS CHILOGNATHA


Superorder Pentazonia
Good autapomorphies:


  1. the last pair of legs (and sometimes also the penultimate and antepenultimate pairs) of the male are modified into clasping organs which hold the female during copulation

  2. the sterna are divided in the midline

Pentazonia are also characterized by a relatively low number of legs: 17-37 pairs in adults. Terga, pleura and sterna are independent. The group includes 3 orders and a total of ca. 350 described species from all parts of the World. One species in Denmark.


Order Glomeridesmida. Unlike other Pentazonia, glomeridesmidans cannot roll up into a sphere. A few cm long. Occur in South and Central America , and in SE Asia.
Order Sphaerotheriida. Giant pill millipedes (da.: kæmpekugletusindben). Up to the size of a golf ball when rolled up. Occur on the southern hemisphere except South America.
Order Glomerida. Pill millipedes (da.: kugletusindben). Rarely more than 7 mm in diameter when rolled up. Occur on the northern hemisphere and SE Asia. One species, Glomeris marginata, in Denmark (shown in RFB: fig. 20-8D, E, p. 712), common in deciduous forest.
Superorder Colobognatha
Good autapomorphies:


  1. mouthparts more or less modified into stiletto-like structures with unknown function

  2. first juvenile stadium hatching from the egg with four pairs of legs (three pairs in other millipedes, see RFB: fig. 20-12F, p. 717)

  3. a parent (the mother in some species, the father in others) protects the eggs by rolling itself around them like in some centipedes (character 9 in the section on centipedes).

The group includes four orders and a total of ca. 300 species, a few cm long, described from all parts of the World.


Order Platydesmida. Mouthparts only moderately modified. Occur on the northern hemisphere and SE Asia.
Order Polyzoniida. Mouthparts strongly modified. Eyes present. Occur in all parts of the World. Polyzonium germanicum (Fig. 14) occurs in Denmark, but is rare.
Order Siphonocryptida. Very similar to preceding order. Four species from SE Asia, the Canary Islands and Madeira.
Order Siphonophorida. Mouthparts stiletto-like (Fig.14). No eyes. Occur in North, Central and South America, South Africa and Southeast Asia. The ruling World Champion in leg numbers belongs here: Illacme plenipes from California (up to 750 legs).
Superorder Nematophora
The name means ‘thread-bearer’, and accordingly a good synapomorphy is:


  1. posterior end with one or more pairs of spinnerets (Fig. 15)

In Nematophora, the sterna are not fused with the pleura. In this character, Nematophora resembles the superorders mentioned above and differs from those treated further down.


The group includes three orders and a total of ca. 1000 described species. Three species are known from Demmark.
Order Stemmiulida. One to two eyes on each side of the head. Body a few cm long, circular in transverse section, tapering posteriorly. No defence glands, but some species exhibit an incredible defensive behaviour, escaping from aggressors in long jumps. Occur in South and Central America, tropical Africa and India.
Order Callipodida. Many eyes. Up to 10 cm long, cylindrical. Defence glands present (smell horrible!). Occur in the warmer parts of the Holarctic region including the Mediterranean region.
Order Chordeumatida. Many eyes (except in some species which are blind). Body a few cm long, often moniliform or with flat ‘wings’ like Merocheta (see below). Occur in all regions. The Danish Nematophora belong here, our commonest species is Craspedosoma rawlinsi which occurs in humid forest soil.
Superorder Merocheta – flat-backed millipedes, da.: kiletusindben
Good autapomorphies:


  1. number of segments almost constant: the vast majority of the species have 19-20 segments1 in the adult (other Helminthomorpha, cf. Fig. 12, have more segments, and the number is often variable within each species).

  2. no eyes (convergent with many subgroups within other superorders)

  3. defence glands with two compartments, produce HCN (mentioned by RFB: 715), this type of glands only occurs in Merocheta.

In most species of Merocheta the body rings (‘segments’) have a pair of keel- or winglike dorsolateral outgrowths, giving the dorsal side a flattened appearance. Using the flat back, the merochetans wedge their way between, e.g., fallen leaves on the ground (RFB: “flat wedgers, p. 714).


Only one order:
Order Polydesmida. Ca. 3000 described species, from a few mm to ca.10 cm long, occurring in all parts of the World. Ten species in Denmark, including several of the genus Polydesmus (pictured without a name on RFB: fig. 20-8C, p. 712).
Superorder Juliformia – cylindrical millipedes, da.: cylindertusindben
Good autapomorphies:


  1. the first body segments, collum, overlaps the posterior part of the head as well as the anterior part of segment 2 (RFB: fig. 20-8F, p. 712)

  2. Spermatozoa with a “bilayered acrosome” (Fig. 2). (A “bilayered acrosome” also occurs in Hexapoda, and loss of one of the ‘layers’, the actin-containing perforatorium, is considered a possible autapomorphy of Myriapoda [char. 8 in the chapter on myriapod relationships]. In Juliformia, a perforatorium ‘re-appears’, but it lacks actin, is called a pseudoperforatorium and is regarded as a novelty ‘invented’ by the common ancestor of Juliformia).

Juliformia constitute the millipedes as typically understood by laymen: long, cylindrical animals with plenty of legs (although the highest numbers of legs occur in colobognathans, cf. above). The defence glands of Juliformia produce benzoquinones – a type of defensive chemical which is widely distributed among arthropods.


The group includes three orders with ca. 4000 described species, 27 species in Denmark. The orders can only be told apart by details in mouthparts and gonopods.
Order Spirobolida. From a few to more than 20 cm long. Do not occur naturally in Europe, but in all other parts of the World. The genus Narceus, mentioned by RFB, belongs here. A small species has been introduced to the greenhouses of the Botanical Garden in Copenhagen where it seems to thrive.
Order Spirostreptida. From a few to 30 cm long. Distributed in the same areas as Spirobolida. The very large Archispirostreptus gigas from East Africa, which is one of the most frequent ‘terrarium millipedes’, belongs here. Some species are pests on peanuts, potatoes etc. in Africa.
Order Julida. Occur naturally only on the northern hemisphere. Rarely longer than 5 cm. Many common Danish species belong here, including the black Julus scandinavius, the brown species of Cylindroiulus, and our largest millipede: Ommatoiulus sabulosus (up to 5 cm, with two yellow longitudinal stripes). Some species, especially the small, thin Blaniulus guttulatus, may be pests on potatoes and sugar beets.
-o0o-
The 16th millipede order, Siphoniulida, is known only from a handful of specimens. It is probably related to Colobognatha or Juliformia.

Millipede phylogeny
Enghoff (1984) presented a cladistic analysis of the millipede orders2. The results are shown in the cladogram, Fig. 12 (and in RFB: p. 716). Numbering of characters in the present chapter follows Fig. 12.
Since 1984, a number of studies on millipede phylogeny have been published, including some using molecular characters. So far, however, the results have not stabilized, and the 1984 model is offered here as, so far, the most robust one.
The class Diplopoda consists of two subclasses: Penicillata, which was characterized above, and Chilognatha (not to be confused with Chilopoda) which is characterized by the following autapomorphies:


  1. cuticle calcified

  2. most diplosegments with a pair of defence glands (not more than one pair, although RFB 813 suggests the opposite); the glands are secondarily missing in, e.g., Chordeumatida.

  3. no trichobothria (cf. character 16 in the chapter on myriapod relationships)

  4. certain muscles and ligaments reduced (in contrast to Penicillata to Penicilalta, where they have been retained)

  5. spermatozoa ‘depressed’, i.e., strongly shortened along the anterior-posterior axis (Fig. 2)

Among the five superorders of Chilognatha, four (Colobognatha + Nematophora + Merocheta + Juliformia = Helminthomorpha on Fig. 12) share an obvious synapomorphy, viz.:




  1. at least one leg-pair on segment 7 in the male is modified into gonopods which serve as copulatory organs.

Nematophora, Merocheta and Juliformia (= ‘Eugnatha’ on Fig. 12) share further synapomorphies, including:




  1. terga and pleura fused into pleuroterga (this fusion has, however, happened convergently in the colobognathan order Platydesmida)

Merocheta and Juliformia are sister-groups, united by the apomorphy:




  1. pleuroterga and sterna fused into complete body rings (RFB: fig. 20-10C, p. 713).

Merocheta and Juliformia are sometimes collectively referred to as ‘ring-forming millipedes’.


On Fig. 2, Polyzoniida branch off before Glomerida. This is in conflict with the 'strong' character 9, and the spermatological evidence on which this part of Fig. 2 is based is accordingly dubious.

CLASS PAUROPODA – PAUROPODS, DA.: PAUROPODER
RFB: 718.
The branched antennae constitute a good autapomorphy for pauropods. The pauropods pictured by RFB belongs to the Tetramerocerata and almost has diplosegments like a diplopod (6 terga for 9 pairs of legs); in Hexamerocerata the number of terga corresponds to the number of legs.
About 500 species of Pauropoda have been described, and one or two handfuls of species are known from Denmark.
Order Hexamerocerata. Many primitive traits are preserved, including tracheae on the first body segment and powerful mandibles. Seven species from Africa and South America.
Order Tetramerocerata. No tracheae, mandibles reduced, weak, number of terga less than number of leg-pairs. In all parts of the World.
IDENTIFICATION KEY TO MYRIAPODA
Classes/orders occurring in Denmark are shown with CAPITAL LETTERS. Orders not occurring in Europe are in (brackets).


Key to the myriapod classes


1.

Most body segments with two pairs of legs. Usually calcified, slow animals

MILLIPEDES, DIPLOPODA



-

One pair of legs per segment

2




2.

Usually more than 1 cm long, brownish/yellowish. A pair of poison fangs behind/below the head

CENTIPEDES, CHILOPODA



-

Smaller than 1 cm, usually whitish. No poison fangs

3




3.

Antennae moniliform, unbranched. Twelve pairs of legs

SYMPHYLA

-

Antennae branched. Nine, rarely 10-11 pairs of legs

PAUROPODA

Key to the orders of centipedes, CHILOPODA


1.

15 pairs of legs

2

-

21 or more pairs of legs

4




2.

Antennae and legs extraordinarily long. Big, composite eyes. Spiracles mid-dorsally

Scutigeromorpha



-

Antennae and legs ’normal’. A small group of single eyes on each side of the head, or eyes missing. Spiracles lateral

3





3.

Large gland openings on coxae of the 2-4 posteriormost leg-pairs. Body relatively compact

LITHOBIOMORPHA



-

No coxal pores on posterior legs. Body relatively slender

(Craterostigmomorpha)




4.

21, rarely 23 pairs of legs

SCOLOPENDROMORPHA

-

29 or more pairs of legs

GEOPHILOMORPHA



Key to the orders of millipedes, DIPLOPODA

(exluding Siphoniulida)




1.

Characteristic tufts of setae (’brushes’) along the sides of the body. Rarely more than 5 mm long

POLYXENIDA



-

No such brushes. Often larger

2




2.

At most 13 segments including telson. Body can be rolled into a sphere

3

-

Adults with more than 17 segments including telson. Body almost never capable of rolling up into a sphere

4





3.

13 segments incl. telson. Ball usually >1 cm in diameter

(Sphaerotheriida)

-

11-12 segments incl. telson. Ball (almost always) <1 cm in diameter

GLOMERIDA



4.

19-20 segments (exceptionally 18 or up to 25). No eyes. Usually with dorsolateral processes rendering the dorsal surface more or less flat. Complete body rings (= tergum + pleura + sternum)

POLYDESMIDA



-

Adults (almost always) with > 20 segments

5




5.

Collum covering the posterior part of the head and the anterior part of segment 2. Body circular in transverse section. Complete body rings (tergum + pleura + sternum)

6


-

Collum smaller, and/or body transverse section not circular. Sternum, sometimes even pleura, independent sclerites

8





6.

Head with a longitudinal suture starting from anterior margin. Gnathochilarium with a very large mentum

(Spirobolida)



-

Head without such a suture. Gnathochilarium different

7




7.

Lateral sclerites of gnathochilarium (stipites) meet in midline. Usualy a few cm long, segments often hairy

JULIDA


-

Gnathochilarial stipites divided by mentum. Usually large animals (> 5 cm). Body hairless

(Spirostreptida)






8.

Collum small, head largely uncovered. Head/mouthparts not attenuated. Eyes usually well-developed. Posterior end with spinnerets (may be difficult to see)

9


-

Anterior end different. Head/mouthparts usually more or less attenuated. At most a few single eyes, often no eyes at all. No spinnerets

11





9.

At most 32 segments. Body transverse section circular or with dorsolateral projections.

CHORDEUMATIDA



-

Adults with >32 segments

10




10.

Up to 10 cm long, eyes well-developed, strongly sculptured segments and often a horrible smell

Callipodida



-

A few cm long, 0-2 single eyes on each side. Weakly sculptures segments, no particular smell. Some species can jump

(Stemmiulida)






11.

Body transverse section semicircular, or depressed semicircular

12

-

Body with large or smaller dorsolateral processes

14




12.

No eyes. Head/mouthparts not attenuate

(Glomeridesmida)

-

A few single eyes. Head/mouthparts attenuate

13




13.

With a mid-dorsal suture

Siphonocryptida

-

No mid-dorsal suture

POLYZONIIDA




14.

Tergum and pleura of each segment fused. Head/mouthparts only slightly attenuate

Platydesmida



-

Pleura separate from tergum. Head/mouthparts often extremely attenuate

(Siphonophorida)


REFERENCES

(only those cited in the compendium)


Baccetti, B., Burrini, G., Dallai, R. & Pallini, V. 1979: Recent work in myriapod spermatology (The spermato­zoon of Arthropoda XXXI). - Side 97-111 i Camatini, M. (red.): Myriapod biology. - Academic Press London etc.
Deuve, T (ed.). 2000: Origin of Hexapods - Mémoires du Muséum national d'Histoire Naturelle (under trykning).
Dohle, W. 1980: Sind die Myriapoden eine monophyletische Gruppe? Eine Diskussion der Verwandtschaftsbeziehungen der Antennaten. - Abhandlungen des naturwissenschaftlichen Vereins in Hamburg (NF) 23: 45-104.
Dohle, W. 1985: Phylogenetic pathways in the Chilopoda. - Bijdragen tot de Dierkunde 55(l): 55-66.
Enghoff, H. 1984: Phylogeny of millipedes - a cladistic analysis. - Zeitschrift für zoologische Systematik und Evolutionsforschung 22: 8-26.
Jamieson, B.G.M. 1987: The ultrastructure and phylogeny of insect spermatozoa. - Cambridge University Press, Cambridge etc.
Kraus, O. & Brauckmann, C. 2003: Fossil giants and surviving dwarfs. Arthropleurida and Pselaphognatha (Atelocerata, Diplopoda): characters, phylogenetic relationships and construction. – Verhandlungen des naturwissenshcaftlichen Vereins Hamburg, Neue Folge 40: 5-50.
Shear, W.A. & Bonamo, P.M. 1988: Devonobiomorpha, a new order of centipeds (Chilopoda) from the Middle Devonian of Gilboa, New York State, USA, and the phylogeny of centiped orders. - American Museum Novitates 2927: 1-30.
Wheeler, W.C., Cartwright, P. & Hayashi, C.Y. 1993: Arthropod phylogeny: a combined approach. - Cladistics 9: 1-39.

LEGENDS TO ILLUSTRATIONS

Fig. 1. The anterior tentorium is an internal skeletal structure which can be viewed as an inward extension of the external surface of the head capsule. The upper scanning electron micrograph shows the the head capsule of a millipede in ventral view; the paired tentoria are aritculated laterally ("tilledningssted"). The lower SEM shows the same head capsule in oblique posterior view. The circular hole in the head capsule is the articulation site of the left antenna. Also notice the tridentate labrum which is characteristic of millipedes.

Fig. 2. Spermatozoan structure in myriapods, after Baccetti & al. (1979). Notice that the branching pattern of the spermatozoan-based cladogram differs from the cladogram recommended in the compendium text (Figs. 6 and 12).

Fig. 3. Sterna, spiracles and tracheal apodemes in millipedes. The upper SEM shows the oval sternum in a species of Juliformia. On both sides, sternum is fused with pleura, the latter hide the tracheal apodemes from view. (In Juliformia the two sterna of each diplosegments are fused but the picture only shows the anterior sternum). The lower SEM shows an isolated sternum of a species of Nematophora. Here the tracheal apodemes are visible; you can perhaps imagine that they project 'into the paper', i.e. into the body.

Fig. 4. Trichobothria in a symphylid (left), a pauropod (center) and a pincushion millipede (right). Notice the swollen basis of the trichobothria which are located in a concavity in the cuticle. Of the remaining part of the trichobothria, only the tips are shown.

Fig. 5. Gnathochilarium in a pauropod (left) and a pill millipede (right). Embryos above, fully developed animals below.

Fig. 6.Suggested relationships within Uniramia (presuming that Uniramia is monophyletic!)

Fig. 7. Relationships within Chilopoda according to Dohle (1985). Numbers refer to synapomorphies mentioned in the text.

Fig. 8. Posterior end of a lithobiomorph centipede. Notice the coxal pores.

Fig. 9. Male gonads in Chilopoda Epimorpha. Geophilomorpha left, Scolopendromorpha right.

Fig. 10. Poison fangs in Geophilomorpha. Notice the undivided coxosternum (cxs) and the direct articulation between the first and the fourth telopodite article (arrow).

Fig. 11. Leg of a symphylid. Notice stylus (arrow).

Fig. 12. Relationships within Diplopoda. Modified after Enghoff (1984). Numbers refer to synapomorphies mentioned in the text.

Fig. 13. SEM of antennal tip of a millipede. Notice the four large sense organs (autapomorphy for Diplopoda).

Fig. 14. Millipedes of the superorder Colobognatha. a-c: Polyzonium germanicum, the only Danish colobognathan. d: a species of the order Siphonophorida. e: anterior end of another species of Siphonophorida; notice the extremely pointed head and the stout antennae.

Fig. 15. A: Craspedosoma rawlinsi, the commonest Danish species of Diplopoda Nematophora. B: posterior end of a species of Nematophora; notice spinnerets (arrow).



Fig. 16. The fossil millipede group Arthropleurida lived in the Devonian, Carboniferous and Permian periods. From Kraus & Brauckmann (2003).

1 Traditionally, segments of millipedes are counted as follows: The four anteriormost segments, which are not diplosegments, are each counted as one. The following segments, which are diplosegments, are also counted as one each. The telson, which is not a segment, is also counted as one. A merochetan millipedes with ’20 segments’ thus consists of the four anterior, simple segments, 15 diplosegments, and the telson (4+15+1 = 20).

2 The Siphonocryptida had not been recognised as a separate order in 1984 but uncontroversially belong in Colobognatha.





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