A phylogram is a branching tree diagram that summarizes in graphic form the evolutionary history of a group of organisms. The length of each branch stem indicates the amount of evolution, typically measured in a quantity like number of nucleotide substitutions, that occured between the connected branch points.

In 1986, Michael M. Miyamoto and Morris Goodman published a phylogram showing the results of their work in estimating the historical evolutionary relationships of a broad selection of eutherian mammals.

Miyamoto, M. M. and Goodman, M. 1986. Biomolecular systematics of eutherian mammals: phylogenetic patterns and classification.
Systematic Zoology 35:230-240.

Below is their published phylogram as drawn by Phyloscope, a JavaScript application developed at the Berkeley Phylogenomics Group. The horizontal lines in the tree are the stems that indicate the amount of evolution along that branch. The spans, the vertical lines, serve only to connect an ancestor to its immediate descendants. The length of the span has no special significance.

A phylogram can be represented as a text string for transfer between software programs and databases. The earliest general format for phylograms is the Newick format, based on the format originally developed in 1984 for the PHYLIP software package for inferring evolutionary trees. Below is the Miyamoto and Goodman phylogram in Newick format that was used to draw this tree.

(Edentata:55, (((Orycteropus:12, Trichechus:43):1, (Procavia:29, (Elephas:18, Loxodonta:5):55):10):15, (((Chiroptera:27, (Tupaia:43, ((Talpa:24, (Suncus:24, Erinaceus:58):6):4, (Manis:5, ((Felis:13, Leo:7):32, ((Canis:37, Ursidae:12):4, ((Phocidae:19, Zalophus:17):7, (Procyonidae:12, Mustelidae:22):9):5):17):13):3):10):6):8, (((Lemuridae:46, (Galago:16, Nycticebus:27):10):8, (Tarsius:15, ((Cebus:10, (Atelinae:5, (Aotus:6, Callithrix:9):3):3):18, ((Hylobates:6, (Pongo:1, (Gorilla:2, (Homo:22, Pan:1):2):6):2):5, (Presbytis:1, (Cercopithecus:1, (Erythrocebus:0, ('Macaca fascicularis':2, ('Macaca mulatta':5, 'Macaca fuscata':0):1, (Theropithecus:2, Papio:4):15):2):1):8):6):9):22):10):13, ((Ochotona:7, Oryctolagus:54):4, (Caviomorpha:107, (Spermophilus:29, (Spalax:23, ((Rattus:71, Mus:19):15, (Ondatra:27, Mesocricetus:32):27):20):8):12):15):11):9):12, ((Sus:50, ((Lama:10, Camelus:24):31, (Hippopotamus:31, (((Ovis:9, Capra:8):19, ((Antilocapra:13, Giraffa:14):7, (Cervus:8, Alces:9):11):2):9, (Tragelaphinae:6, ('Bos grunniens':6, (Bison:5, 'Bos taurus':15):7):11):6):47):10):19):18, ((('Equus (Asinus)':6, 'Equus caballus':31):24, (Tapirus:19, Rhinocerotidae:23):11):22, ((Phocoena:4, Tursiops:17):5, (Balaenoptera:36, Eschrichtius:2):8):29):12):12):16):55);