Grzimek's Animal Life Encyclopedia - Many drawings have been added in addition to some distribution maps and revisions to species accounts. A 17-volume set. print ed., 2nd edition, 2003 location 

Encyclopedia of Whales, Dolphins and Porpoises by Erich Hoyt 2017 Firefly Books location 

Grzimek's Animal Life Encyclopedia: Evolution - 2011 paper edition location

Grzimek's Animal Life Encyclopedia: Extinction - 2013, 2 volumes paper edition location

Encyclopedia of Animal Behavior - 2010 3 volumes, from Elsevier

Nature Encyclopedia
Oxford University Press, 2001 location 
6500 entries, some with colored illustration and some biographical, are found in this work with contributions from specialists in the United States or Great Britain. Entries are generally concise and some topics are "featured articles" (photosynthesis, food chain, coral reef, fungus, angiosperms, for example). Sections at end provide: a cross-disciplinary chronology beginning with prehistoric times of 15,000 million years ago and almanac/world's record-like ready reference tables of facts on natural places or phenomena such as mountains, clouds, deserts, waterfalls, oceans, volcanoes, earthquakes, land areas of countries, greenhouse gas emissions, rarest trees, most invasive species, for example. A brief synopsis of different classification system overviews is also found here.   

The Oryx Guide to Natural History: the earth and all its inhabitants
Oryx Press, 1999
On the general and popular side. location 

Encyclopedia of Entomology
An A to Z arrangement of entries is found in this 4-volume set published by Springer. Topics covered include: major taxa of insects, their morphology, physiology, genetics, behavior, ecology and evolution, microbiology and pathology, interactions with humans, pesticides and pest management, arthropods, and notable biographies. 2nd ed. 2008 paper ed. location 

A Dictionary of Zoology
The 4th edition of this dictionary was published in 2014 by Oxford University Press. Edited by Michael Allaby. location 
An online edition is also available A Dictionary of Zoology. 3rd ed., 2009.

Encyclopedia of Evolution
Oxford University Press, 2002, 2 volumes location 
All sorts of articles are found in this work, with covered topics among the 370 signed entries including subject-based as well as biographical, historical, and overview essays. There is much to commend this source, although the jump from the Topical Outline of Articles to the corresponding alphabetically-arranged articles is not obvious in some cases. Advisors include Sarah B. Hrdy, Richard Leakey, John Maynard Smith, and Edward O. Wilson and contributions by Yale faculty members. 

Animal: the definitive visual guide to the world's wildlife
DK Publishing, Inc., 2001 location 
A one-volume encyclopedia of the animal kingdom, replete with color photographs of many of the 2000 species featured, invertebrates to vertebrates, common and rare. Entries include distribution maps, habitat information, and interesting facts. Written by specialists in zoology, biology and nature.
 

Encyclopedia of the World's Zoos
Fitzroy Dearborn Publishers, 2001 location 
A 3-volume set with signed articles generally a few pages in length, explaining many topics related to zoos around the world, organizations and persons of note, and issues of interest to all in this field. Many of the articles end with a list for further reading, often citing publications not well known. Note: a historical related title has recently been added. See Zoo: a history of zoological gardens in the West, Reaktion, 2002 location 

Encyclopedia of Fish Physiology: from genome to environment
3 volumes, Elsevier Inc., 2011 location 

Turtles & Tortoises of the World
Blandford Press, 1998 location 
A source with many photos, a bibliography for further reading, and a number of distribution maps.
 

The Encyclopedia of Mammals
Facts on File, Inc., 2nd ed. 2006 3 volumes paper ed. location 
David W. MacDonald, (a professor in the Dept. of Zoology at University of Oxford) also credited with an earlier well-received mammal encyclopedia, edits this work. Reference works consulted are listed in the bibliography. The color illustrations and special feature articles (How Dolphins Keep in Touch, Social Life of Rabbits, Bushmeat Trade, for example) and somewhat more generalist tone distinguish this from Walker's Mammals of the World.

Grzimek's Encyclopedia of Mammals 5 volumes McGraw-HIll 1998 location 1  location 2 

Pelagic Dictionary of Natural History of the British Isles by Peter J. Jarvis. c2020 location 

Darwin's Fishes. An Encyclopedia of Ichthyology, Ecology, and Evolution by Daniel Pauly. Cambridge University Press, c2004. This book explores Charles Darwin's connections to fish. The main section is an alphabetical arrangement. Includes a lengthy bibliography. paper ed. location 

Book of Snakes: A Life-Size Guide to Six Hundred Species From Around the World by Mark O'Shea. University of Chicago Press/Quarto Publishing plc, c2018) Includes index of common names, glossary, bibliography. location