SEGMENTED PROTOSTOMIA (after Ruppert & Barnes 1994 p. 1052, Brusca & Brusca 1990 p. 683)

                      =========== ANNELIDA & RELATIVES (segmented worms)
                      |
<<=OTHER PROTOSTOMIA==|   ==O==== ONYCHOPHORA (velvet worms; fossil Hallucigenia)
                      =P==|
                          ==R================================== TO ARTHROPODA ===>

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade): P: a) elongate body of many similar segments** b) ventro-lateral appendages c) must molt to grow d) ectodermal cilia lost e) extensive hemocoel ('open' circulatory system), coeloms reduced f) heart with openings to hemocoel (ostia) g) tracheal system for respiration h) oblique striated muscles i) larval prototrochal cilia lost j) larval apical ciliary tuft lost O: a) external segmentation suppressed b) unique oral papillae c) lobopod limbs

R: a) lateral compound eyes b) two tagmata (head, trunk) c) calcification of cuticle d) fully segmental sclerites (body-wall cuticular plates) e) each body segment has 2 sclerites (dorsal tergum, ventral sternum) f) jointed appendages with intrinsic muscles g) complete loss of motile somatic cilia/flagella (some sperm retain flagella) h) hemocyanin respiratory pigment

                                         ==A========= Arachnida (spiders, mites, scorpions, etc.)
                                    ==C==|
   ========= CHELICERATA ===========|    ==X========= Merostomata (horseshoe crabs)
   |                                |
   |                                ===P============= Pycnogonida (sea spiders)
   |
<<=|   ===== TRILOBITOMORPHA ======================== (extinct trilobites)
   |   |
   |   |                                       ====== Symphyla (symphylans)
   |   |                                  ==S==|
   |   |                                  |    ====== Chilopoda (centipedes)
   |   |                ===Myriapoda======|
   =T==|                |                 =========== Diplopoda (millipedes)
       |                |
       |  == 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): CHELICERATA: a) two tagmata (cephalothorax=prosoma, without distinct head; abdomen=opisthosoma)** b) mouth lies before segment 1 embryologically c) segment #1 limbs= chelicerae (no antennae; may be pincer-like or fangs) C: a) cephalothorax has a carapace shield b) 1st or 2nd abdominal segment modified as genital somite P: a) pre-oral proboscis b) ovigers (unusual 3rd pair limbs) c) abdomen reduced or absent d) long, 9-segmented walking legs e) multiple pairs of gonopores on some/all legs f) loss of compound eyes A: a) abdominal limbs reduced, lost, or modified as spinnerets b) loss of compound eyes X: a) enlarged cephalothorax w/ large carapace b) abdominal limbs modified as book gills c) long, spiked telson T: a) mouth lies before segment 2 embryologically b) segment #1 limbs= antennae c) 4 pair post-oral head segments with biramous limbs similar to thoracic limbs TRILOBITOMORPHA: a) 3 tagmata (cephalon, thorax, pygidium) b) body dorso-ventrally flattened c) limbs of post-oral head segments similar to limbs of thorax (all with two branches, biramous?)**

M (Mandibulata): a) 2 tagmata (head, trunk of many similar segs.)** 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 UNIRAMIAÝ (= Tracheata, = Atelocerata): a) second antennae lost b) mandible is 'whole-limb' c) unique tracheal system d) uniramous limbs (exopodite lost) Myriapoda: a) 2 tagmata (head, trunk of many similar segs.)** b) loss of compound eyes c) loss of palps on first & second maxillae d) repugnatorial glands S: a) medial fusion of both pairs of maxillae b) maxillipeds modified as raptorial poison fangs Hexapoda: a) second maxillae fuse as labium b) 3-segment thorax with limbs c) 11-segment abdomen, no limbs Entognatha: a) mouthparts sunk in a pouch Ectognatha: a) mouthparts not sunk in pouch Pterygota: a) possess wings on 1 or 2 thoracic segs. Ý a unique translocation of mitochondrial leucine transfer RNA is shared by insects & crustaceans, but not myriapods, and suggests the Uniramia may be paraphyletic (Boore et al. 1998, Nature 392:668)

       ====1============================= Cl. Remipedia
<<==C==|
       |   ===3========================== Cl. Cephalocarida
       =2==|
           |   ==5======================= Cl. Branchiopoda (fairy shrimp, water fleas, etc.)
           =4==|
               |   ==7=================== Cl. Maxillopoda (copepod, ostracod, barnacle, etc.)
               ==6=|
                   |    ==8============== SubCl. Phyllocarida (Or. Leptostraca)
                   =Mal=|
                        |   =====10====== SubCl. Hoplocarida (mantis shrimps)
                        ==9=|
                            |       ==11= SupOr. Peracarida (mysids,  amphipods, isopods, etc.)
                            ==Eumal=|
                                    ==12= SupOr. Eucarida (krill, shrimps, lobsters, crabs, etc.)

TRAITS SUPPORTING EACH CLADE (** plesiomorphic- a primitive state, not unique to clade): C (Crustacea): a) first antennae uniramous** b) second antennae biramous c) mandible is simple (gnathobasic) d) sessile (non-stalked), compound eyes** e) many similar, biramous, phyllopodous thoracic limbs** f) telson with rami g) nauplius larvae 1: a) first antennae biramous b) raptorial mouth appendages c) segment #6= maxilliped d) many similar trunk segments (no trunk tagmata) with paddle-like biramous legs e) pre-antennal process f) eyes lost 2: a) 3 tagmata (head, thorax, abdomen) b) reduced number of body segments 3: a) abdominal appendages lost b) abdomen of 11 segments c) segment #5= leg-like d) compound eyes lost 4: a) fully developed carapace b) abdomen has fewer than 9 segments 5: a) maxillae (segments #4 & #5) reduced or absent (trunk segment number & limbs vary greatly) 6: a) thorax has fewer than 11 segments b) abdomen has fewer than 8 segments 7: a) thorax has fewer than 7 segments b) abdomen has fewer than 5 segments c) unique naupliar eyes & loss of lateral compound eyes

Mal (Cl. Malacostraca): a) thorax of 8 segments with similar limbs b) abdomen of 7 segments + telson c) carapace covers head & thorax** d) first antennae biramous e) stalked eyes f) gills on thoracic limbs 8: a) second antennae uniramous b) abdomen of 7 segments + telson** c) second maxilla like thoracic limbs** d) similar, phyllopodous thoracic limbs** 9: a) abdomen of 6 segments + telson b) thoracic limbs stenopodous c) long muscular abdomen d) telson lacks rami 10: a) carapace covers head & 4 thoracic segments b) limbs of first 5 thoracic segments uniramous & subchelate c) thorax segment #2 with very large subchela d) moveable rostrum e) gills on pleopods Eumal (Subcl. Eumalacostraca): a) carapace covers head & thorax (primitively)** 11: a) carapace not fused with all head & thorax segments** b) thoracic oostegites form brood chamber c) pre-juvenile manca stage 12: a) carapace fused dorsally with all head & thorax segments b) 3 pair maxillipeds (except euphausids) c) last 5 pair thoracic limbs uniramous (except euphausids) d) well-developed gills under carapace (except euphausids) e) brood eggs on pleopods (except euphausids)

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