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

                      =========== ANNELIDA (segmented worms)
                      |
<<=OTHER PROTOSTOMIA==|   ==O==== ONYCHOPHORA (velvet worms)
                      =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)

O: a) external segmentation suppressed b) unique oral papillae c) lobopod limbs d) tracheal system 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 cilia/flagella (except some sperm)

                                         ==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 without distinct head, abdomen)** 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 UNIRAMIA (= Tracheata, = Atelocerata): a) 2° 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 1° & 2° maxillae d) repugnatorial glands Myriapoda: a) 2 tagmata (head, trunk of many similar segs.)** b) loss of compound eyes c) loss of palps on 1° & 2° maxillae d) repugnatorial glands S: a) medial fusion of both pairs of maxillae b) maxillipeds modified as raptorial poison fangs Hexapoda: a) 2° 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.

       ====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) 1° antennae uniramous** b) 2° antennae biramous c) mandible is simple (gnathobasic) d) sessile (non-stalked), compound eyes** e) many similar, biramous, phyllopodousthoracic limbs** f) telson with rami g) nauplius larvae 1: a) 1° 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) 1° antennae biramous e) stalked eyes f) gills on thoracic limbs 8: a) 2° antennae uniramous b) abdomen of 7 segments + telson** c) 2° 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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