Jacob Theodor Klein (nickname Plinius Gedanensium; 15 August 1685 – 27 February 1759) was a German jurist, historian, botanist, zoologist, mathematician and diplomat in service of Polish King August II the Strong.
Klein was born on 15 August 1685 in Danzig (Gdansk) in Poland. Klein studied natural history and used his position as the secretary of the city to found a botanical garden there (now called Ogrod Botaniczny w Oliwie). His son-in-law was Daniel Gralath, a physicist who would become mayor.
Klein dealt with small matters of zoological nomenclature and set up his own system of classification of animals, which was based on the number, shape, and position of the limbs. For his work in the field of natural science, Klein had been awarded the membership of several scientific societies, including the Royal Society in London and the Danzig Research Society. He was also a correspondent of the Lutheran pastor Friedrich Christian Lesser. He died 27 February 1759 in Konigsberg, Prussia (now Kaliningrad, Russia).
Naturliche Ordnung und vermehrte Historie der vierfussigen Thiere. Schuster, Danzig 1760
Vorbereitung zu einer vollstandigen Vogelhistorie. Schmidt, Leipzig, Lubeck 1760
Stemmata avium. Holle, Leipzig 1759
Tentamen herpetologiae. Luzac jun., Leiden, Gottingen 1755
Doutes ou observations de M. Klein, sur la revue des animaux, faite par le premier homme, sur quelques animaux des classes des quadrupedes & amphibies du systeme de la nature, de M. Linnaeus. Bauche, Paris 1754
Ordre naturel des oursins de mer et fossiles, avec des observations sur les piquans des oursins de mer, et quelques remarques sur les belemnites ... Bauche, Paris 1754
Tentamen methodi ostracologicae sive Dispositio naturalis cochlidum et concharum in suas classes, genera et species. Wishoff, Leiden 1753
Quadrupedum dispositio brevisque historia naturalis. Schmidt, Leipzig 1751
Historiae avium prodromus. Schmidt, Lubeck 1750
Mantissa ichtyologica de sono et auditu piscium sive Disquisitio rationum, quibus autor epistolae in Bibliotheca Gallica de auditu piscium, omnes pisces mutos surdosque esse, contendit. Leipzig 1746
Historiae piscium naturlais promovendae missus quartus de piscibus per branchias apertas spirantibus ad justum numerum et ordinem redigendis. Gleditsch & Schreiber, Leipzig, Danzig 1744
Summa dubiorum circa classes quadrupedum et amphibiorum in celebris domini Caroli Linnaei systemate naturae. Leipzig, Danzig 1743
Naturalis dispositio echinodermatum. Schreiber, Danzig 1734
Descriptiones tubulorum marinorum. Knoch, Danzig 1731
An Tithymaloides. Schreiber, Danzig 1730
