(onychopheran) |
The PANARTHROPODA
(= arthropods & nearest relatives) (tree and traits from
|
(tardigrade) |
===========O=== Onychophora (velvet worms; fossil Hallucigenia) | <<=======P==========| ====T=== Tardigrada (water bears) ===1===| ====A=== TO ARTHROPODA ====================>
Back to Zool 250 tree for animal phyla or Protostomia
b) ventro-lateral legs (lobopods) with hooked tips c) must molt to grow d) chemical makeup of cuticle (alpha-chitin and non-collagenous protein) e) ectodermal cilia lost f) extensive hemocoel ('open' circulatory system) g) coeloms reduced to nephridia & gonads h) heart with openings to hemocoel (ostia) i) panarthropodan sensilla j) paired, segmental, saccate nephridia b) unique oral papillae c) possess tufted & unbranched tracheae b) tri-partite cerebral ganglia (proto-, deuto-, & tritocerebrum) (Harzsch 2004 Evol. & Dev. 6:303) c) loss of circular muscle layer |
b) loss of nephridia c) 4 pair stubby, uniramous, unjointed or weakly jointed legs d) claws of anterior legs modified into stylets & stylet supports e) tri-radiate, myo-epithelial sucking pharynx f) eutelic development b) 4 pair median ocelli c) two tagmata (head, trunk) d) calcification of cuticle e) fully segmental, articulated sclerites (body-wall cuticular plates) f) each body segment has 2 sclerites (dorsal tergum, ventral sternum) g) two-part appendages: basal protopod & distal, multisegmented part (telopod) h) complete loss of motile somatic cilia/flagella (some sperm retain flagella) i) unique hemocyanin respiratory pigment j) larva with 3 pair of appendages k) 6 pair of saccate nephridia (4 in head, 2 in trunk) |
(tree and traits from
Back to Zool 250 tree for animal phyla or Protostomia
(pycnogonid sea spider)
(horseshoe crab)
(true spider)
Phylum ARTHROPODA
Ruppert et al. 2004 p. 540, 720, and
Brusca & Brusca 1990 p. 485, 538, 589, 598, 659, 683, 691;
taxa in FULL UPPER CASE indicate the four arthropod subphyla)
(diplopod myriapod)
(chilopod myriapod)
(extinct trilobite)
===P=========== Pycnogonida (sea spiders)
|
==============CHELICERATA================| ==X======= Merostomata (horseshoe crabs)
| ==E==|
| ==A======= Arachnida (spiders, mites, scorpions, etc.)
|
<<=| ==========TRILOBITOMORPHA=========================== (extinct trilobites)
| |
| | ========== Symphyla (symphylans)
| | ==S==|
| | | ========== Diplopoda (millipedes)
| | ===Myriapoda===|
=T==| | =============== Chilopoda (centipedes)
| |
| =======UNIRAMIA====| =====Entognatha=== Collembola (springtails)
| | | |
| | ==Hexapoda==| == Thysanura (silverfish and firebrats)
| | (Insecta) =====Ectognatha=|
=M=| == to Pterygota (winged insects) ===>
|
======= TO CRUSTACEA =======================================================>
TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade):
b) cephalothorax= acron + 7 segments with legs c) seg.#1 lost (no antennae) d) mouth lies before segment 2 embryologically e) seg.#2 limbs= chelicerae (pincer-like or fangs) f) seg.#3 limbs= palps or pedipalps g) gonopores on abdomen segment #2 h) compound eyes b) ovigers (unusual 3rd pair limbs) c) abdomen (=opisthosoma) reduced or absent d) long, 9-segmented walking legs e) multiple pairs of gonopores on some/all legs f) compound eyes lost; 4 median ocelli on turret b) 1st or 2nd abdomen segment= genital somite c) 2 median eyes b) abdominal limbs modified as book gills c) long, spiked telson d) segmental nephridia share a common pore b) 2nd prosomal segment legs= pedipalps c) compound eyes lost (living spp.); modified to 5 pairs of single eyes b) segment #1 limbs= antennae c) 4 pair post-oral head segments with biramous limbs similar to thoracic limbs b) body dorso-ventrally flattened c) limbs of post-oral head segs. similar to limbs of thorax (all with 2 branches, biramous?)** |
b) 5 pair head appendages (2 pair antennae, 1 pair mandibles, 2 pair maxillae) c) body segment cuticle of 4 sclerites (tergum, 2 lateral pleura, sternum) d) mouth anterior to segment 3 in adult e) ommatidium has crystalline cone & cornea b) mandible lacks palps c) paired segmental trachea & spiracles associated with terrestrial life d) uniramous limbs (exopodite lost) e) 2 pair segmental nephridia (segs. #4 & #5) or lost b) no median ocelli; compound eyes loosely spaced c) loss of palps on first & second maxillae d) repugnatorial glands b) 3-segment thorax with limbs c) 11-segment abdomen, no limbs
|
$ new evidence suggests Myriapoda branched off before the Hexapoda and Crustacea diverged (e.g., these two groups both have a 4-part crystalline cone in their ommatidia but myriapods do not; Harzsch 2004 Evol. & Dev. 6:303), so Myriapoda may be a separate subphylum (i.e., subphylum Uniramia is rejected).