Appendix I. Characters and Conditions for Animal Phylogeny

Don't be too rigid about these categories, but assign them according to general pattern across most species belonging to a particular taxon. The particular characteristics are roughly organized by priority for sorting animals at the higher taxonomic levels, then proceed down to finer and finer distinctions within particular groups.
 

Body symmetry

* asymmetrical, radial, bilateral or secondarily radial
(The first three categories are exactly parallel to cell-tissue organization: cellular level, two fundamental tissues layers - diploblastic, or three fundamental tissue layers - triploblastic)

Embryology

* cleavage: radial, spiral, peripheral, or otherwise modified

* cleavage: determinate (= mosaic) or regulative (indeterminate)

* fate of blastopore (if one forms!): mouth, anus, or closed over before mouth or anus forms

* origin of the body cavity (if any) between gut and body wall: formed from the blastocoel, formed by a split in mesodermal disks, formed from outpocketings of the archenteron, or some other process
 

Body Covering

* non-living, chemical cuticle entirely covers the exterior, and must be shed to grow + chemical that makes up most of the cuticle: collagen, or chitin
+ thickness or rigidity of the cuticle: thin cuticle, or exoskeleton * external, calcium carbonate spines, plates or shell, covering large areas and growing by addition at edges as animal grows

* epidermis:

+ syncytial and absorptive (used to take up food)
+ permeating a non-living matrix (lorica) that grows with the body and is not shed,
+ living cells exposed directly to the (aquatic) environment,
# ciliated in some surface areas, or not
# strengthened by dermal (bony) scales
+ covered by thickened, dead cells that are frequently replaced by living cells underneath # dead cells formed into distinct scales, or not
# follicles in epidermis absent, form hair, or form feathers  

Digestive Tract

* absent, secondarily lost, "blind" (no anus), or complete (anus present)

Body Cavity Type (in adult)

* lined with peritoneum (eucoelom or "true" coelom)

* unlined and not an extension of circulatory system (pseudocoelom)
* unlined and connected to circulatory system (hemocoel)

+ whether or not a remnant of lined cavity occurs in gonads or other organs

Metamerism

Whether or not body is metameric; if so:

* which body structures are repeated

* way in which metameres are formed in the embryo or juvenile

+ simultaneously, with number fixed, or

+ successively, just in front of pygidium, and numbers variable.

 * whether or not several metameres are combined into tagmata
 

Appendages

* present, or not

If present:

* spines or scales, only; rigid or movable
+ made of cilia inside cuticle, or otherwise * fleshy parapods with embedded chaetae   * lobopods (covered with cuticle, with terminal claws)

* jointed appendages with exoskeleton

+ number and arrangement of separately muscled, walking leg branches and segments

+ number, shape, and enervation of head appendages

+ number and arrangement of appendage pairs per body unit

 * pectoral and pelvic pairs of fins + with or without movable support rays * two pairs of lobed or jointed appendages, with endoskeleton includinjg humerus and femur

Life History Stages

* whether or not marine members of the taxon have planktonic larvae + whether larvae swim by cilia, movable appendages, or flexible tail and fins

+ if ciliated, whether or not larvae have a mouth and feed, or do not

 * for primarily terrestrial, parasitic, or freshwater taxa, whether or not development is direct or indirect + if indirect, numbers and kinds of distinct, immature stages * whether they have, and if so what kinds of, diapause and cyptobiotic capabilities

* notable tendencies to retain juvenile or embryonic features in adults (paedogenesis, neoteny)
 

Reproductive Patterns

(These characters are often highly variable within taxa, and only generally useful as main trends across most species belonging to a taxon.)

* gonochoristic or hermaphroditic, and if hermaphroditic:

+ protandric or protogynous

+ self-fertilization possible, or not

 * whether fertilization is internal or external (often correlates with whether egg is shelled or not)

* whether embryos develop in utero or external to female (oviparous); if in utero:

+ whether maternal nutrition is provided during development (viviparous), or embryo relies entirely on yolk laid down at or before fertilization (ovoviviparous)

+ if external, whether parents care for young after hatching, or not

 * whether or not parthenogenetic; if parthenogenetic:
+ males occur, or not

+ if males occur, whether they are haploid or diploid

+ whether or not sexual eggs or embryos are especially resistant to phyical stresses

* position, number and form of genitalia and accessory sexual organs
 

Central Nervous System

* no nerve cells, nerve net, nerve ganglia, or cephalic ganglia form a brain

* longitudinal nerve cords absent,  or present

+ if present, how many and where (dorsal, lateral, ventral), they are
 

Respiratory System

* if marine or freshwater:
+ gills present or absent

+ blood circulated through them or not


* if terrestrial:

+ air exchange through the skin, only, or
+ tracheal system present, or

+ esophageal lungs present, or
 

^ relative size and complexity of lungs

^ structure of glottis


^ lung ventilation controlled by oral, chest wall or diaphragm muscles

^ oscillating or once-through (parabronchii) air flow

^ sound production by larnyx, syrinx, or other means

  + book lungs present, or

+ pulmonary mantle cavity

Circulatory System

* present or absent, if present:
+ open or closed system


+ one heart present, multiple hearts, or no heart
+ if one heart, number and arrangement of separate chambers


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Last modified on November 4, 2003